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 Topic: 7
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A sales tax of 7% 2016-12-07
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?

20 million as a percentage of 7.3 billion 2015-11-18
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.

A 4 by 7 array 2015-10-27
From star:
don breaks a 4x7 array into a 2x7 array and another array.what is the fact for don's second array
Seven switches with 3 stages each 2015-09-15
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.
Is 22/7 is an irrational number? 2015-06-07
From Sayak:
Is 22/7 is an irrational number
A 7 person golf schedule 2014-02-21
From Claude:
Golf Holiday: 7 guys, play a 4-some and a 3-some 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 4-somes and 3-somes.
A 7% solution 2014-01-14
From imran:
what amount of H2SO4 should be added to make 5mL of 0.7% H2SO4 solution
12 golfers for 7 rounds 2013-09-25
From Dennis:
I have 12 golfers playing a round of golf for seven days. How can I set-up teams so that everyone plays with everyone at least once in those seven days. Thanks!
A schedule for 2, 7 team divisions 2013-09-24
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.
6 golfers in threesomes over 7 rounds 2013-09-24
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?
7 golfers, a threesome and a foursome 2013-09-04
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.

The multiplication table for the different bases 2013-02-01
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.
Golf for 17 2013-01-23
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.
A puzzle with a triangle and 57 2012-04-25
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 -

 0 0 0 0 57 0 0 0 0 0

Any ideas ? this has to be in in just over 24 hrs ......help!

Golf for 17 2012-03-29
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?

A golf holiday 2011-01-04
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.
6 rounds of golf 2010-11-29
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.

The difference of the two numbers 2010-02-15
From Steve:
The difference of the two numbers 'abcdef ' and ' fdebca ' is divisible by 271. prove that b = d and c = e.
Holiday for 7 golfers 2010-01-05
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.
Sandra's age 2009-09-24
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?
A base 7 number and a base 9 number 2009-07-09
From koteawarao:
Find a base 7 three-digit number which has its digits reversed when expressed in base 9.

ans: (281) base 7 and (182) base 9

7 digit combinations 2009-05-11
From CAROL:
I NEED TO KNOW HOW MANY 7 DIGIT COMBINATIONS FROM 0-9 THERE ARE WITHOUT ANY REPEATES, OR WHAT THOSE COMBINATIONS ARE?
0123456789 2009-03-25
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?"

7 golfers playing 4 days of golf 2009-01-30
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.
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 2008-11-13
From natalie:
draw four possible arrays for 72 marbles
A 7-digit odd number 2008-06-26
From Godryk:
I am the smallest 7-digit odd number. my ones digit is the sum of my thousands, and ten thousands digits. What number am I?
How many combinations of 8614 are divisible by 7? 2008-01-22
From Rebecca:
How many combinations of 8614 are divisible by 7 equally (with no remainder)?
Base seven 2007-05-19
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.
A 3-digit number in base 7 has its digits reversed when expressed in base 9. 2007-01-28
From Ashley:
A 3-digit number in base 7 has its digits reversed when expressed in base 9. Find this number.
Divisibility by 7 and 11 2004-10-13
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!
Digits in the decimal expansion 2004-02-11
From Leslie:
In the decimal expansion of 1/17 what digit is in the 1997th place?
37 with four 4'2 2004-01-03
From Myra:
Using four fours and only four fours to get an answer of 37.
Divisibility by 7 2003-11-14
From A student:
how do you test a number to see if it is divisible by 7 or not?
The units digit of 57 to the 28th power 2003-09-01
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?

Making 7 2002-11-26
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.
27 2001-09-10
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.
The best of 7 2001-09-08
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
```

1234567890 2000-09-14
Can you find two whole numbers, with the smallest possible difference between them, which when multipled together equal: 1234567890?
Rule of 78 2000-03-22
From Dan Baumgarten:
Can you explain the rule of 78 and the reverse rule of 78? Thanks.