







Four equations in 3 unknowns 
20150823 

From damien: solve:
S x U  T = 44
T  U x S = 36
U + T  S = 7
U x U / S = 4 Answered by Penny Nom. 





20 golfers playing four rounds 
20150817 

From Paul: I have a party of 20 golfers playing four rounds in fourballs.
I realise that everyone will have 7 players that they do not play
with, however I want to ensure that no one plays with the same
person twice and that the Captain plays with the 12 players of
his choice. Answered by Victoria West. 





The game of 24 
20150121 

From aaron: 24 game whants me to use 11 14 5 and 9 to make 24 allowed (+  dividing and multiplying) Answered by Penny Nom. 





4 rounds of golf as three foursomes 
20140818 

From Christopher: For our golf trip, we will be playing 4 rounds of golf as three foursomes. We would like to have each person play with everyone at least once. Is this possible? Answered by Victoria West. 





1÷[1√2(order of surd is 4)] 
20140502 

From Anoushka: if t=1÷[1√2(order of surd is 4)] , then t=? Answered by Penny Nom. 





Four digit phone numbers 
20140225 

From Tom: Hi, I'm an online math teacher, working on lessons for my students.
This question is in their book and I can't do it...! Help!
It has to do with phone numbers, and in this problem,
we are only dealing with
the last 4 digits of the number.
It asks how many possible numbers we have
if at least one digit repeats in the last 4 digits of the number. Answered by Penny Nom. 





Four tangent circles 
20131009 

From Nilesh: Four circular cardboard pieces, each of radius 7cm are placed in such a way that each piece touches two other pieces. How to find the area of the space enclosed by the four pieces?
Please let me know. Answered by Robert Dawson. 





Four equations 
20130808 

From may: HI how to solve this 4 equations?
A+C = 0
4A+B8C+D=1
3A+16C8D=29
12A+3B+16D=5 Answered by Robert Dawson. 





Four circles 
20130529 

From varsha: four circular cardboard pieces each of radius 7cm are placed in such a way that each piece touches two other pieces. find the area enclosed by the four pieces. Answered by Penny Nom. 





Four digit combinations starting with 7 6 
20130515 

From Kaye: How do I find the rest of a four digit combination starting with 7 6? Answered by Penny Nom. 





A 4 digit code 
20130326 

From chris: I saw a previous question about a 4 digit code type thing and I was wondering if you could email me that same type of thing.
I changed the pin number on my phone's lock screen and I tried hard to remember it, then I had to go help my mom with something and I automatically forgot it and there is no way for me to get back on my phone.
I need all of the possible 4 digit number combinations without the numbers 0, 1, or 2. It cannot be repeating, ascending, or descending.
I know you may not want to do all of them, but I really need it. Answered by Robert Dawson. 





f(x) + f ''''(x)=0 
20130305 

From Andreea: Hei. I don’t speak lot of english but here is my question,hope u understand: f(x) + f ````(x)=0. so, my question. what is f(x), where f ````(x) is f(x) derivative by four time ? i tried to find the answer and i knew f(x) is something like that f(x)=e^x*sinx but miss something. Answered by Brennan Yaremko. 





Four digit "combinations" using 0124 
20130227 

From Ayana: What are all the possible four digit combinations using 0124. Please list them for me. Thank you. Answered by Penny Nom. 





The zeros of a fourth degree polynomial 
20130123 

From Dakota: My problem has multiple steps and I have done everything but the last one. 8The original problem is f(x)=x^45x^3+7x^2+3x10 and I have to find the zeros of the equation. I used synthetic substitution like my teacher taught us to get the equation of x^33x^2+x+5=0 but now I don't know how to get the zeros of that equation, or solve it. Answered by Penny Nom. 





A 4 digit phone lock using the digits 4, 2, 3 and 0 
20121224 

From Ragu: I would like to know formula for searching a combination of 4 digit. eg.
I knew my Phone Lock combination is my car plate number 4230. But
this time, i used another way around instead of 4230.
But I am sure, there is only this 4 digits only. 4 & 2 & 3 & 0 Answered by Penny Nom. 





Some 4 digit numbers 
20121025 

From samira: How many 4digit numbers are there in which the first and last digits are the same? Answered by Penny Nom. 





A four digit number 
20121009 

From cyndi: find this 4 digit number: the tens digit is 1/3 of the hundreds digit; the 2 digit number formed by the tens and ones digits i the largest prime number smaller than 40; the sum of all 4 digits is the same as the number of face on an icosahedron ? what is the number? Answered by Penny Nom. 





Four tangent circles 
20121004 

From renu: inside of a circle K of radius length measure R,three circular discs A,Band C each of radius r are placed so that each touches the other two and K . express R in terms of r. in the space between K, A and B , another circular disc D is placed which just touches K, A and B. if the radius is s, show that (6+root3)s=(2+root3)r Answered by Penny Nom. 





Four digit combinations from 1,2, ..., 9 
20120226 

From Errol: show me a list with all four digit combination numbers from 0 9 Answered by Penny Nom. 





A four digit number 
20110916 

From gina: i am having a hard time figuring this out.. i believe the answer is 3105 but the 0 is throwing me off... i am a 4 digit number between 3100 and 3200, none of my digits are even, the sum of my digits is 9, the largest digit is in the ones place, what number am i ?? Answered by Penny Nom. 





Two line segments in the plane 
20110815 

From Tim: For this problem I actually have tried to visualise the image in my head many times. This question makes my head spin.
Four points lie in a plane. They are partitioned into two pairs so that the sum of the lengths of the segments joining the points of each pair has the minimal possible value.
Prove that these segments have no common points. Answered by Chris Fisher. 





The game of 24 
20110506 

From shaylin: how do you use 3,9,7,9 once in any operation equal to 24? Answered by Penny Nom. 





1 and four eights inches 
20110201 

From Miranda: WRITING TO EXPLAIN:If a line is measured as 1 and four eighth inches long,explain how you could simplify the measurement? Answered by Penny Nom. 





Golf pairings 
20101217 

From AL: I have a golf tourney where we have fourteen players and are playing five times/rounds of golf. I am trying to pair up two threesomes and two foursomes so we don't play with the same person twice or the least amount of times. Answered by Victoria West. 





What numbers can I be? 
20101113 

From john: my thousands digit is 2 times my ones digit.my hundreds digit is my ones digit plus 2. my tens digit is the difference between my thousands and hundreds digit what numbers can i be? Answered by Penny Nom. 





Fourdigit numbers using 0,3,4,5,6,and 7 
20101112 

From Katy: Using only the digits 0,3,4,5,6,and 7, how many distinct fourdigit numbers exist that are greater than 4002 and less than 6732? Answered by Stephen La Rocque. 





The area of a 4 sided region 
20100714 

From Cliff: If I wanted to know the square footage of an area that has four different sides and only had the length of one side and the angles at the ends of that length; could the other lengths be found if I wanted to have a total of 130,680 square feet? Answered by Robert Dawson and Tyler Wood. 





Four digit numbers 
20100522 

From tyeisha: Whats all the four digit numbers you can come up with using numbers 09 Answered by Tyler Wood. 





The game of 24 
20100220 

From haley: hello.... we have these very hard make 24 stumpers. i am stuck on one.... how can you make 24 using the numbers 771318?? thanks! Answered by Claude Tardif. 





Expressing the natural numbers in terms of 4 fours. 
20100119 

From Steve: When I was studying mathematics, there were several of us that tried to express the natural numbers in terms of 4 fours. Allowing the use of any known math operation, for example n to the zeroth power is 1.Is there more info on this exercise. This was done mentally, nothing written down. Answered by Robert Dawson. 





Holiday for 7 golfers 
20100105 

From Andy: I am having difficulty scheduling pairings for a forthcoming Golf holiday. There are 7 players and we will be playing 7 rounds  each round will be a 3 ball and a 4 ball. I am trying to work out a schedule that means everyone plays with each other roughly the same number of times (with a minimum of, say, 3 times if possible). Also, we are looking to ensure everyone plays in roughly the same number of 3 and 4 balls. Any suggestions would be much appreciated (we leave in 10 days time). Thank you. Answered by Victoria West. 





Four digit numbers with no repeats 
20100102 

From Daniel: I want to know how many different numbers there would be between the numbers
00009999 that do not have any numbers that duplicate or repeat in the number? For example
the first number would have to be 0123 and the last would be 9876 (I think) Thanks! Answered by Penny Nom. 





Four fours 
20091129 

From linda: Four Fours order of operations challenge i need problems using 4's only that have an answer of 13, 18, and 19
than you Answered by Penny Nom. 





Four consecutive odd integers 
20091024 

From Tonya: the sum of four consecutive odd intergers 2008 what are the intergers Answered by Penny Nom. 





Game of 24 
20091002 

From trami: game of 24 by using 4 7 7 1? Answered by Claude Tardif. 





Game of 24 
20090924 

From vanessa: Using the following numbers 13,6,6, and 12 to equal 24. Using 5th grade math Answered by Penny Nom and Claude Tardif. 





A fourdigit positive integer 
20090904 

From TRACEY: I AM A FOURDIGIT POSITIVE INTEGER SUCH THAT THE SUM OF MY DIGITS IS 18 AND MY DIGITS REVERSED ARE EXACTLY FOUR TIMES GREATER THAN MYSELF. WHAT NUMBER AM I? Answered by Robert Dawson. 





The game of 24 
20090827 

From ANITA: Help I'm suppose to be a math expert, yet I can not yield 24 from the numbers 8,4,9,9, using each only once. HELP Answered by Penny Nom. 





The game of 24 
20090826 

From melvi: how can you get the numbner 24 but only useing the numbers 7,5,4,5 Answered by Penny Nom. 





Fourth and fifth degree polynomials 
20090820 

From Evin: hello.i am a student . ax^4+bx^3+cx^2+dx+e=0 x=? i want to learn the solution or formula of equations of the fourth and fifth degree...PLEASE Answered by Robert Dawson. 





Game of 24 
20090522 

From Sam: Using the numbers 7, 3, 2, and 2, how do you get the number 24? Answered by Claude Tardif and Harley Weston. 





Fourdigit combinations 
20090418 

From Carri: How many 4digit combinations can be made out of digits 1, 2, 3, 4, & 5 using each number once? What are the combinations? Answered by Penny Nom. 





A foursided lot 
20090412 

From Robert: back of property is 137' across,with an angle of 122deg.on the left side and an angle of 140 deg. on the right side,the left side is 123' and the right side is 93' long,the left front is 130 deg. and the right front side is 150 deg. and the front of the property measures 78' Answered by Harley Weston. 





Fourdigit numbers 
20090411 

From jp: How many fourdigit numbers are there? Answered by Penny Nom. 





Game of 24 
20090405 

From Ramona: math 24 using 16, 9, 20, 7 Answered by Penny Nom. 





Four digit numbers 
20090310 

From Theresa: I need to know the number of 4 digit numbers that can be formed using 1234 without repeating numbers Answered by Penny Nom. 





The game of 24 
20090301 

From Jeff: My son in the 5th grade was given a problem for extra credit and could use parents help. He was given the numbers 21, 13, 9, 6 and asked to use each number only once by +, , /, x the numbers in any order to obtain an answer of 24. Answered by Harley Weston. 





A four digit number 
20090212 

From alex: the number of tens plus the number of hundreds equals the number of thousands.
the number of ones is half the number of tens and one more than the number of hundreds the hundreds digit is 2. what is this four digit number Answered by Penny Nom. 





Four digit numbers using 1, 0, 2 and 8 
20090127 

From Mike: How many combinations of this four digit number 1028 can this produce only using those numbers. Example would be 0000, 0001,0002,0008,0010,0011,0012,0018,etc... Answered by Penny Nom. 





Three consecutive natural numbers 
20090126 

From abby: 1.what is the smallest fourdigit number that is the sum of the three
consecutive natural numbers? what are the three consecutive
natural numbers that give this sum?
2.what is the largest three digit number whose square root is a prime? Answered by Penny Nom. 





A four digit passcode 
20090112 

From john: i have a machine at home that has a four digit passcode and the numbers range from 1 to 4 how can i get all the ways those numbers can be used Answered by Harley Weston. 





The game of 24 
20081124 

From Davey: this has us all stumped. 5 ,5 ,7 ,and9 = 24. Oh may you assist in ending
our brain pain Answered by Penny Nom. 





Forming 10 from 4 fours 
20081106 

From Corderro: I need a answer for 10 using only the number 4 Answered by Penny Nom. 





The product of the digits of a four digit number 
20080726 

From Pete: I am a student preparing for a competition and this was one of the prep problems: The product of the digits of a four digit number is 6x5x4x3x2x1. how many such numbers are there with this property? Answered by Stephen La Rocque. 





Four fours 
20080625 

From jen: Use four 4's and some of the symbols: +,,X, / and (), to give expressions for the whole numbers from 0 through9. Example : (4X4+4)/4=5 Answered by Janice Cotcher. 





The game of 24 
20080410 

From sherwin: ok is like this you must get 24 using 1,5,5,5 but you can only use +,  , / and * Answered by Claude Tardif. 





The game of 24 
20080401 

From Frank: Hi, my name is Frank. I have been really stumped on this 24card. It has the 4 # of 21,3,5,10. If you have any suggestions, I would be grateful! Answered by Claude Tardif. 





I am a 4digit number 
20080212 

From Nickie: I am a 4digit number with no repeating digits. I am divisible by 5, my first two digits (left to right) make a number divisible by 3, and my first three digits make a number divisible by 4. Also, my digits have a sum of 19 and I have the digit 7 in the thousands place. Who am I? Answered by Penny Nom. 





Four digit numbers containing 85 
20080206 

From Vonda: How many four digit numbers contain the digit pattern 85 at least once and only once? Answered by Stephen La Rocque. 





The game of 24 
20080206 

From Jameeka: What is a solution for 10,11,9 and 2 (Using fractions) in the game 24 square. Answered by Penny Nom. 





The game of 24 
20080117 

From Raina: I have four numbers 3 3 9 5 that need to equal 24 using addition subtraction multipliction and division and I'm so stuck. Answered by Chris Langdon, Stephen La Rocque and Claude Tardif. 





The game of 24 
20071119 

From M: Please help...how would you compute 2,2, 6, and 9 to equal 24? Answered by Penny Nom. 





The game of 24 
20071117 

From Todd: Hello. My son is very good at the Math 24 game and when he is stumped,
I am usually able to figure it out. However, we are both stumped with
this one. The numbers are 6, 6, 9 and 5. You can use addition, subtraction,
division and multiplication. Please help us equal 24 with those 4 numbers. Answered by Claude Tardif. 





Four digit odd numbers 
20070926 

From sonia: how many 4 digit odd numbers can be made using the digits 2, 5, 7, and 8 Answered by Penny Nom. 





Four digit combinations 
20070904 

From Natalie: Using The Numbers 7 4 5
How many different 4digit combinations are possible, you can use any of the numbers twice. Answered by Penny Nom. 





The digital lock for a cell phone 
20070829 

From Hollie: i have a four digit lock code on my cell phone and cannot remember what it is. i know that it does not contain a 2 or a 4 and none of the numbers are repeated. the numbers range from 0 to nine and the only way to figure out what the code is, is to try randomly. I was wondering if you could give me a list of possible combinations using the information i gave you to make it easier to crack the code. Answered by Penny Nom. 





Four fours 
20070823 

From Belinda: My son came home with a math question that I can figure out. He needs to use only the number 4 and only four 4's, no less no more.
The problems need the answers 11,13,14,and 18. He can use any mathematical sign except square root. He's been able to get all but these
so far and I've worked them, but can't come up with the problems. Can anyone help? Answered by Stephen la Rocque. 





Four digit numbers 
20070730 

From Spence: My son has a problem that he has been unable to figure out. I was asked to
try, but I am confused on how to get the last two parts. Any help would
be great.
Thanks
Spence
How many fourdigit numbers can be formed under each condition?
A) The leading digit cannot be zero: 9(10)(10)(10)=9000
B) The leading digit cannot be zero and no repetition of digits
allowed: 9(9)(8)(7)=4536
C) The leading difit cannot be zero and the number must be less
than 5000: ??
D) The leading digit cannot be zero and the number must be even:
?? Answered by Penny Nom. 





24 fourdigit numbers 
20070421 

From Megon: Of the 24 fourdigit numbers formed from the digits 1,2,3,&4 is there an easier way to find their sum other than writing them all out and totaling them by hand? Answered by Stephen La Rocque. 





A four digit number 
20070328 

From Paulo: Hi , if i have to discover a keypad number of four digit , Which the closest combination of getting right?? i have this tips > i know the second and thirth number is odd . dont have the number 7 in any digit ,
Doesnt begin with 8 or 4 ... and dont have the 2 as a last number .
Thanks !! Answered by Stephen La Rocque. 





The game of 24 
20070309 

From colleen: We are playing the 24 math game where four numbers need to combine using any sign (+,  X, \) to equal 24. The four numbers are 22, 21, 6, 20. Answered by Penny Nom. 





Four digit numbers 
20070226 

From Anton: Hello! I would like to ask you how many combinations are possible using 4 digit number. # # # # (1...9).There is no zero,numbers don't repeat,second and forth are odd.Thanks Answered by Penny Nom. 





Four 9s 
20061215 

From A student: Can you make 67 with four 9's without using the ceilling method? Answered by Stephen La Rocque. 





Four digit combinations 
20061026 

From Sasha: CAN YOU LIST ALL OF THE POSSIBLE 4 DIGIT COMBINATION'S, THAT DO NOT START WITH 0? Answered by Stephen La Rocque. 





Four fours 
20061008 

From Prabh: Find out 10 BEDMAS problems using order of operation with only four 4's in the problem. The solution must be the digits 110.
Example 44/44=1 Answered by Stephen La Rocque. 





Four 4's 
20060910 

From Ying: How can I use 4 four times, use any mathematical signs, such as +, , times, division, ( ), !, square root to get answer 33, 41, or 45? Answered by Stephen La Rocque. 





Twenty golfers 
20060508 

From Mona: We have twenty golfers and four rounds of golf. We would like to figure out how to make foursomes so that each golfer plays with as many different golfers as possible. Answered by Penny Nom. 





9, 8, 7 and 2 in the game of 24 
20060317 

From Alana: I just began student teaching in a 5th grade math class and found that the students play 24 in class, a game that I used to play in elementary school. The students choose a card which shows 4 numbers and then have to use any combination of addition, subtraction, multiplication, and division to reach 24. There was one card that we found that seems to have all of us stumped. The four numbers are 9, 8, 7 and 2. Can you figure out how to make 24 with those? Thanks so much for your help! Answered by Claude Tardif. 





The game of 24 with 7, 5, 5 and 4 
20051218 

From Nicole: i was playing the 24 game the other day. you get 4 digits and you have to turn them into 24. You can use addition, subtraction, division, and multiplication. You have to use all the numbers but you can only use each number once. an example is 2 4 4 1 the answer is (2x4)(41)=24. I got stuck on one. The numbers were 7 5 5 4 . Answered by Penny Nom. 





The game of 24 
20051010 

From Kim and Chris: My 4th grade son came home with a math game called 24 game. In it each card has 4 numbers on it. Each number can only be used once, in any order, using multiplication, subtraction, division, or addition. We are stuck on one and wondered if you could help. The four numbers are: 9, 9, 9, 9. And they must equal 24. Any clues? Answered by Claude Tardif. 





The game of 24 
20050110 

From Manny: HI  my daughter and I are being driven crazy by the following "24" question 7,7,3,3. She's good at the game (well, better than I am) and her teacher gave her this one. Any insight would be appreciated! Answered by Claude Tardif. 





The game of 24 
20040916 

From Angelica: how can you make 24 out of 7,7,6,5? Answered by Claude Tardif. 





The game of 24 
20040914 

From Alan: I was playing that math 24 game and i cant get 21,14,2,2 to equal 24 Answered by Claude Tardif. 





The 24 game 
20040909 

From Erik: Ive spent around 40 hours on this one problem. I need help. 3,3,7,7 Answered by Claide Tardif. 





The game of 24 
20040604 

From Samantha: i have the game 24 (the one where you have to use multiplication, division, addition, and subtraction to get to the answer 24) I was playing when i came across the 4 numbers 20, 17, 7, 11 and i cant seem to get 24. Answered by Claude Tardif. 





37 with four 4'2 
20040103 

From Myra: Using four fours and only four fours to get an answer of 37. Answered by Claude Tardif. 





Four digit combinations 
20031231 

From A student: i need all 4 digit combinations using 09 please Answered by Penny Nom. 





Four digit numbers 
20031120 

From Rob: Hello, I sure hope you can answer this question. I got into a discussion at work about how many possible combinations there are for a four digit number using the numbers 0 through 9. This was in reference to a discussion about the lottery. I said there was only 10,000 possible combinations. My friend said that there was many times more, but he could not remember how to figure it out. The answer and the formula would be greatly appreciated. Answered by Penny Nom. 





The 4th difference 
20031117 

From Jack: If i had a sequence which was the same at the 4th difference, aka difference
to the 4th, like:
1 5 14 30 56 96
(sequence)
4 9 16 26 40
5 7 10 14
2 3 4
1 1
then what would be the set formulars to find out a, b, c, d, and e
as i know the equation has to be an^{4}+bn^{3}+cn^{2}+dn+e Answered by Penny Nom. 





The game of 24 
20030903 

From A student: We have a game where four numbers must equal 24 using addition, subtraction, multiplication and/or division.Ý I am stuck on the following four numbers  12, 24, 9 and 17. Answered by Penny Nom. 





Two sequences that agree in the first 4 terms 
20030526 

From A student: Is it possible to have two formulas that define sequences that agree on the first four terms but not the rest? Answered by Penny Nom. 





Four digit palindromes 
20030505 

From Heather: How many palindromes were in between the numbers 1000 and 9999? Answered by Penny Nom. 





4 x abcd = dcba 
20021120 

From A student: Say you have a four digit number (e.g. abcd) and you multiply the number by 4. The answer you get will be the reverse order of the number you started with (dcba). What is the number? The four digits (a,b,c,d) cannot be the same number or cannot be repeated. Answered by Penny Nom and Claude Tardif. 





The 24 game 
20021116 

From Michael: Hello, my name is Michael and I am in elementary school .. We have a game we play in math class called 24 game. In it each card has 4 numbers on it. Each number can only be used once, in any order, using multiplication, subtraction, division, or addition. We are stuck on one and wondered if you could help. The four numbers are 109164. And they must equal 24. Any clues? Answered by Penny Nom. 





The four colour theorem 
20021027 

From Rhonda: is there an actual equation for the four colour map theorem??? i cannot find it anywhere!! if so can you give a breif description on how it works!! Answered by Penny Nom. 





Use a 4 four times 
20020912 

From Amanda: The question is what is if you can only use a 4 four times and get the answer 12, 10, and 6 Answered by Claude tardif. 





Sequences that agree on their first four terms 
20020516 

From Mike: Are there two formulas that define sequences that agree on their first four terms, but differ on the fifth term and all succeeding terms? Answered by Chris Fisher. 





The square root of four 
20020413 

From Frank: In a recent quiz we where asked the square root of four. The quizmaster gave the answer as not only 2 but also 2. Being pedantic I queried this. Although 2 squared is 4, does it follow that the root of 4 is 2 Can you enlighten us? Answered by Claude Tardif and Penny Nom. 





All four eights in three consecutive hands 
20020401 

From Blair: What are the odds against the same person holding all four eights in three consecutive hands. Answered by Brian Alspach. 





Some 5 card hands 
20020328 

From A student: From a standard deck of cards how many 5 card hands are possible consisting of a. exactly 4 hearts
b. two cards of one kind and three of another(like a full house). Answered by Penny Nom. 





100 from four 9's 
20020327 

From A student: My teacher gave us a math problem to try and figure out and I am stumped. The problem was this.... by only using four nines, how can you get an answer of 100? You can add, subtract, multiply or divide...anything you need to do ,but you can only use four nines. Answered by Leeanne Boehm. 





Double square roots 
20020217 

From Ali: i have a question about how to do double square roots with variables and powers. example : v/"" v/"" 81y^{8} Answered by Harley Weston. 





Making 24 
20020117 

From Renee: My 4th grade daughter and I need to find a simple math sentence using 5, 5, 3, & 7 to equal 24. You can add, subtract, divide or multiple. Answered by Penny Nom. 





4 digit combinations 
20010922 

From Laura: I need all of the 4 digit combinations using the numbers 09. Answered by Harley Weston. 





Fourier transform 
20010807 

From Adbul:
 Sir, we have the Dirichlet's condition for the Fourier transform : " The function should be integral over the real line " But why we are we neglecting this for example when we take the Fourier transform of an impulse train?
 Suppose we want to travel from one corner of a square of side 'a' to the diagonally opposite corner. We can travel along the sides which gives a pah length of '2a'. We can also do it in steps as shown below:
_  _PATH  _ _____
Suppose The step size =DELTA x Then the path length will be again '2a'. Now in the limit DELTA x >0 again we get '2a' But when we take the limit we get the straight line diagonal whose length is 'SQRT(2)X a' Where did I go wrong? Answered by Chris Fisher. 





Securing a plank in four dimensions 
20010606 

From Becca: If it takes two nails to secure a plank from rotating on a wall in the third spatial dimension, how many nails would it take if you were attempting to secure the board from rotating in the fourth spatial dimension? Answered by Walter Whiteley. 





Four digit numbers from 1,2,3,4,5,6,7,8 
20010531 

From Katie: Okay.......here's my question...how many different ways can you form a four digit number out of these digits..1,2,3,4,5,6,7,8? This is how my teacher said to do this.... 8*8, 7*7,6*6,5*5,4*4,3*3,2*2,1*1. then she said to add up the products and to multiply by 7. is this correct, and if not how can you figure this out. Answered by Penny Nom and Claude Tardif. 





Five fourths 
20010408 

From Linda: Can you have 5/4 of something? Answered by Penny Nom. 





A four dimensional object 
20010214 

From A student: Can you give me some examples of a four dimensional object you can find around your house? Answered by Harley Weston. 





Four crayons 
20010110 

From Neyra Espinoza: You have four crayons (red, blue, yellow, green). If you line them up, how many different combinations can you get? Answered by Patrick Maidorn. 





4digit numbers using 7, 8, 9 and 0 
20000913 

From Ryan: Could you please help me with the following problem, How many different 4digit numbers are there that use each of the digits 7,8,9,and 0? Please list them. Answered by Penny Nom. 





4 Color map Theorem 
20000602 

From Rick Slen: I am challenging my students to find a map that can not be coloured using only 4 colours. I know that it is not possible, but one boy drew a map with a "country" totally surrounding all the others so of course it touched all other colours. How do I explain that this type of map is not permissable? Answered by Denis Hanson. 





Is a sheet of paper 2dimensional? 
20000306 

From Jaclyn Evans: One day, we were discussing 3dimensional items. Is a sheet of paper considered a 3dimensional shape? Or is it 2dimensional as described by 8.5 by 11 size? Also, could you give me an example of a 4dimensional item or scenario? Answered by Harley Weston. 





Four fours 
19990909 

From Roger: I need help with a math problem my child asked me about I guess in her 7th grade math class they were told to come up with a answer from 110 only using four 4's and she got stuck on the problem that needs to be equal to ten, she asked me and I couldn't help her it's sad so if you could give me the problem and and answer so i could explain it to her I would really appreciate it. Answered by Penny Nom. 





Measuring the fourth dimension 
19990607 

From Suzanne Hall: Hi! The other day, two of my students asked a very interesting question: Is the fourth dimension measured with hypercubes? Their reasoning went like this: Lines are 1D and are measured with line segments, which are part of a line. Planes are 2D and are measured with squares, which are part of a plane. Space is 3D and is measured with cubes, which are part of space. So, logically, hypercubes would be used to measure the fourth dimension. Answered by Chris Fisher. 





Four Corners Maths Problem 
19990216 

From Helen Williams: I am currently a student teacher in the UK and I have to write a 1000 word report on the following maths problem which I am completely stuck on! PLease HELP!! Choose and 3 by 3 section of the hundred square. Add the total of the four corners. How many different groups of four numbers can you find that add up to that number? eg, Total of 4 corners add up to 48. Adding 2, 13, 22, 11 also make 48 etc.. How many different groups of 4 numbers would add up to 48? How would these results compare with thoses obtained from a 3 by 3 square in which the numbers are consective? eg, PLEASE HELP AS I AM COMPLETELY STUCK? WHY DO ALL THESE DIFFERENT WAYS ADD UP TO THE SAME NUMBER?? Answered by Harley Weston. 





Grade 4 curriculum 
19990209 

From John: My daughter is in grade 4 and her math teacher has asked her to write out the number 1 to 10,000. She is currently at 4567 and is sick of it. When I complained that this was not a usefull exercise she said that the Ministry of Education curriculum requires this and gave a photocopy of the page. It states: "read and write whole number to 10,000 in standard, expanded, and written forms (eg., 9367=9000+300+60+7 = nine thousand three hundred sixtyseven). Has the teacher interpreted this the wrong way? Thanks John PS. Do you have a web address for Ontario Math and Science Teachers organization? Answered by Jack LeSage. 





The Fourth Dimension 
19980524 

From Whitney Page: Okay, here goes all my effort to try to explain shat I'm trying to ask of you. It's about something I read in a book called A WRINKLE IN TIME, by Madeline L'Engle. It's called tesser, or tesseract. It talks about first diminsion, a straight line, second diminsion, a flat square, and third diminsion, a square with sides, front and back, top and bottom. I can picture all of that. Then it says that fourth diminsion is when you square the three diminsional square. It also described the fourth diminsion as time. I can't figure out how that can be. Then it says... Answered by Chris Fisher. 

