







A sales tax of 7% 
20161207 

From Kenneth: Hello:
If a sales tax of 7% is placed on every $1.00 of merchandise for sale, is it correct to indicate
the tax as 7%/ per $1.00 or 7%/$1.00? If the calculation is expressed as 7%/$1.00 X $5.00,
the tax is not $0.35 but 0.35. Is a tax rate of 7% incorrectly represented as 7%/$1.00
since the dollar unit cancels from the multiplication?
I thank you for your reply. Answered by Penny Nom. 





20 million as a percentage of 7.3 billion 
20151118 

From Nick: Based on the estimate of the worlds current population (7.3 billion people), I'm trying to work out what percentage of that figure 20 million people would amount to?
(Apologies in advance that I've no idea if the 7.3 billion figure is an American Billion or UK billion)
Thanks for any help.
Nick. Answered by Penny Nom. 





A 4 by 7 array 
20151027 

From star: don breaks a 4x7 array into a 2x7 array and another array.what is the fact for don's second array Answered by Penny Nom. 





Seven switches with 3 stages each 
20150915 

From jeff: We are trying to solve a combination problem. If I have 7 things that can be in 3 states (say on/partially on/off), and all 7 have to a state. How many different combinations can there be? It doesn't seem like we should treat it as 21 independent things, but not sure how to break the problem apart. Answered by Penny Nom. 





Is 22/7 is an irrational number? 
20150607 

From Sayak: Is 22/7 is an irrational number Answered by Penny Nom. 





A 7 person golf schedule 
20140221 

From Claude: Golf Holiday: 7 guys, play a 4some and a 3some each day for 10 days.
Want to have the best balance of each player playing with every other player
the same number of times and each player playing in an equal number of
4somes and 3somes. Answered by Victoria West. 





A 7% solution 
20140114 

From imran: what amount of H2SO4 should be added to make 5mL of 0.7% H2SO4 solution Answered by Penny Nom. 





12 golfers for 7 rounds 
20130925 

From Dennis: I have 12 golfers playing a round of golf for seven days. How can I setup teams so that everyone plays with everyone at least once in those seven days. Thanks! Answered by Victoria West. 





A schedule for 2, 7 team divisions 
20130924 

From Sampson: I'm looking to set up a weekly schedule within a 22 week segment of 2 7 team divisions where every team plays every other team in their divison 3 times and have 4 cross over games with 4 of the other 7 teams in the other division. I've yet to figure this out.
Thanks for your time. Answered by Victoria West. 





6 golfers in threesomes over 7 rounds 
20130924 

From David: I have 6 golfers, (2 threesomes) who will be playing 7 rounds of golf. What is the best way to pair the 6 players so they play with as many different players over the 7 rounds? Answered by Victoria West. 





7 golfers, a threesome and a foursome 
20130904 

From Scott: I'm leading a golf trip with 7 guys, and we're playing 5 rounds of golf together with a threesome and a foursome at each course..
I want to set up a schedule where each person plays at least two rounds with each of the other 6 guys.
Is that possible? I can't seem to find the right combinations.
Thanks for your help! Answered by Victoria West. 





The multiplication table for the different bases 
20130201 

From sylvia: I am having a difficult time trying to figure out how to fill in the multiplication table for the different bases. i don't know how to get the numbers. Answered by Penny Nom. 





Golf for 17 
20130123 

From Richard: I have looked through the examples on your site but can't find one that suits. I am fiddling with one to see if I can get a result; but not confident.
I have 17 players playing 6 rounds in 3 groups of 4 and 1 group of 5. Two players will not be included in any 5 ball group. Can you help me please. Answered by Victoria West. 





A puzzle with a triangle and 57 
20120425 

From sharon:
Question from sharon, a parent:
We have been battling with this for days and cant find any solution 
Using each of the following numbers once, fill all the spaces in the triangles so that each side of the triangle adds up to 57
numbers are 11,12,13,14,15,16,17,18,19
diagram is 
Any ideas ? this has to be in in just over 24 hrs ......help! Answered by Chris Fisher. 





Golf for 17 
20120329 

From Richard: Hi Guys,
I have a scheduling problem which I don't think you have covered before.
Apologies if you have!
I have 17 golfers due to play 4 rounds of golf.
Each round will consist of 3 threeballs and 2 fourballs (ie. 17 golfers in 5 groups)!
Is it possible to come up with a schedule where each golfer plays
with different partners in each round? Answered by Robert Dawson. 





A golf holiday 
20110104 

From Andy: You kindly responded to a question I previously sent with regard to a Golf Holiday and I wonder if I might ask another question please. There are now 7 players playing 5 rounds of golf and I wonder if it is possible to devise a schedule where everyone plays with each other a minimum of two times i.e. they will play twice with some and three times with others. As always, many thanks for your kind assistance. Answered by Victoria West. 





6 rounds of golf 
20101129 

From Andy: I wonder if you are able to assist me with scheduling pairings for a
forthcoming Golf Tournament ?
There are 7 players and we will be playing 6 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. Also, we are looking to ensure everyone plays in roughly the
same number of 3 and 4 balls. Any suggestions would be much
appreciated  thank you. Answered by Chris Fisher. 





The difference of the two numbers 
20100215 

From Steve: The difference of the two numbers 'abcdef ' and ' fdebca ' is divisible by 271. prove
that b = d and c = e. Answered by Claude Tardif. 





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. 





Sandra's age 
20090924 

From cindy: Sandra is more than 20 years old and less than 60 years old. You can count by 7's to reach Sandra's age. Next year you will be able to count by 5's to reach Sandra's age. How old is Sandra? Answered by Penny Nom. 





A base 7 number and a base 9 number 
20090709 

From koteawarao: Find a base 7 threedigit number which has its digits reversed when expressed in
base 9.
ans: (281) base 7 and (182) base 9 Answered by Harley Weston. 





7 digit combinations 
20090511 

From CAROL: I NEED TO KNOW HOW MANY 7 DIGIT COMBINATIONS FROM 09 THERE ARE WITHOUT ANY REPEATES,
OR WHAT THOSE COMBINATIONS ARE? Answered by Penny Nom. 





0123456789 
20090325 

From Dr.: Many years ago I discovered that there are 33 numbers which,
when multiplied by 0123456789, simply rearrange the digits. Surprisingly
(to me at least) is the fact that the digits of all of those 33 numbers add up
to one of the 6 "cardinal" numbers 1, 2, 4, 5, 7, and 8. For example
6 + 2 = 8 and 62 X 0123456789 = 7654320918 etc.
Another interesting (to me) fact is that only the cardinal numbers
1, 2, 4, 5, 7, and 8 rearrange the digits in the number 9876543210.
My question is: "Is this known to anyone but me and the people I have
told?" Answered by Robert Dawson. 





7 golfers playing 4 days of golf 
20090130 

From Trish: I have 7 golfers and we are playing 4 days of golf. I would like to do pairings so that everyone gets to play with each other at least one time. Can you help with this? Not a math whiz here and looking for help. Thank you. Answered by Victoria West. 





Ambitious 7th Grader 
20090128 

From John: I have been asked to tutor a 7th grader who is very good in math. He is taking the most advanced course that his school offers to 7th graders. This course will cover Algebra 1 over a period of two years, using McDougal Littell's Algebra, Structure and Method, Book 1, a book I like a lot.
I have been hired not to help him with his schoolwork, which is too easy for him, but to guide him through something in math beyond his schoolwork. This was his idea, an idea which surprised his parents, but one which they support.
Do you have a suggestion for me? If so, I would be very grateful to hear from you. I think this could be a lot of fun for me and my new student, if I pick the right path.
Thanks and best regards,
John
John Answered by Robert Dawson, Victoria West and Walter Whiteley. 





Arrays of 72 marbles 
20081113 

From natalie: draw four possible arrays for 72 marbles Answered by Penny Nom. 





A 7digit odd number 
20080626 

From Godryk: I am the smallest 7digit odd number. my ones digit is the sum of my thousands, and ten thousands digits. What number am I? Answered by Penny Nom. 





How many combinations of 8614 are divisible by 7? 
20080122 

From Rebecca: How many combinations of 8614 are divisible by 7 equally (with no remainder)? Answered by Penny Nom. 





Base seven 
20070519 

From Dan: A number X is converted to base 7 and becomes a four digit number. Its leftmost digit is removed and written again as the rightmost digit. The number thus obtained is twice X. Find the decimal representations of all such numbers X. Answered by Penny Nom. 





A 3digit number in base 7 has its digits reversed when expressed in base 9. 
20070128 

From Ashley: A 3digit number in base 7 has its digits reversed when expressed in base 9. Find this number. Answered by Penny Nom. 





Divisibility by 7 and 11 
20041013 

From Tammy: I'm stuck in class in Yr 7 And I'm finding it hard on our new topic Divisibility! When I try to find out what this means on Internet sites i can not understand the used symbols like algebra and so on. I'm stuck on the divisibility rules for the number 11! Answered by Penny. 





Digits in the decimal expansion 
20040211 

From Leslie: In the decimal expansion of 1/17 what digit is in the 1997th place? Answered by Penny Nom. 





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. 





Divisibility by 7 
20031114 

From A student: how do you test a number to see if it is divisible by 7 or not? Answered by Penny Nom. 





The units digit of 57 to the 28th power 
20030901 

From Maria:
If 57 is raised to the 28th power, what must be the units digit in the result? If you raise 7 to the 500th power, what is the numeral that will appear in the units digit position? Answered by Penny Nom. 





Making 7 
20021126 

From Bill: At one time I had the answer to this math equation but I have lost it and can't seem to regain it. I may be going at it wrong but as I recall there were the numbers 1 through 4, and the std operators, +, , /, *, and parentheses. The object was to make the four numbers with the operators equal to 7. Each number and operator may be used only once. My 9 year old loves these quizzes but I can't give it to her if I can't provide the correct answer. Answered by Claude Tardif. 





27 
20010910 

From Kacy: In class we were given this problem. We have the numbers 30, 29, 19,11,26. these numbers = 27 in some way but how? the numbers can be applied any way using +  / X ( ) but can only be used 1 time each. can you please help me. Answered by Claude Tardif. 





The best of 7 
20010908 

From Michelle: Professional basketball, hockey, and baseball championships are decided on the best 4 out of 7 games. The first team to win four games wins the championship. In how many possible ways could the team win the championship series after winning the first game?
Example:
Game 1 2 3 4 5 6 7
Result W L L W W W
Answered by Leeanne Boehm. 





1234567890 
20000914 

From Bradley Kloetzly: Can you find two whole numbers, with the smallest possible difference between them, which when multipled together equal: 1234567890? Answered by Harley Weston. 





Rule of 78 
20000322 

From Dan Baumgarten: Can you explain the rule of 78 and the reverse rule of 78? Thanks. Answered by Claude Tardif. 





Root 17 is Irrational 
19990121 

From John Murdock: If you could help me out with this I would appreciate it. Prove that the square root of 17 is irrational. Answered by Harley Weston. 

