Question

At the dance, the ratio of the number of girls to boys is 7:5. If there are 36 more girls than boys, how many girls were at the dance? How many boys were at the dance?

Answer 1

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Answer:

• 126 girls
• 90 boys

Explanation:

The difference is 7-5 = 2 "ratio units", corresponding to a difference of 36 dancers. Then each "ratio unit" stands for 36/2 = 18 dancers.

There are 7×18 = 126 girls.

There are 5×18 = 90 boys.

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You could solve this by writing some equations:

g/b = 7/5

g -b = 36

Then you could substitute for g:

(36+b)/b = 7/5

36/b +1 = 2/5 +1 . . . . expand the fractions

36/b = 2/5 . . . . . . . . . subtract 1

b = (5/2)(36) = 90 . . . multiply by 5/2b

g = 36+90 = 126