SOLUTION: A class consists of equal numbers of boys and girls. Two-fifths of the class are 13 years old and the rest are 14 years old. Three-quarters of the children aged 13 are girls. What

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Question 1180192: A class consists of equal numbers of boys and girls. Two-fifths of the class are 13 years
old and the rest are 14 years old. Three-quarters of the children aged 13 are girls. What
fraction of the total class are 14-year-old boys?

Found 2 solutions by Boreal, MathTherapy:
Answer by Boreal(15235) About Me  (Show Source):
You can put this solution on YOUR website!
x is total number of children
(2/5)x are 13, and 3/4 of them or (3/10)x altogether are girls
(3/5)x are 14, and we know that (2/10)x or (1/5)x of them are girls to make them 50% of all the students. 3/5*x=2/10 or 1/5. That means 1/3 of the 14 year-olds are girls (because (3/5)(1/3)=1/5, so 2/3 of the 14 year-olds are boys.
Can check assuming 120 in class, 60 boys and 60 girls
48 are 13 and 72 are 14
36 are girls 13, so 24 girls have to be 14.
24 is 1/3 of 72, so the boys are 2/3 of the 14 year-olds.

Answer by MathTherapy(10551) About Me  (Show Source):
You can put this solution on YOUR website!

A class consists of equal numbers of boys and girls. Two-fifths of the class are 13 years
old and the rest are 14 years old. Three-quarters of the children aged 13 are girls. What
fraction of the total class are 14-year-old boys?
The other person is WRONG!
2%2F5 of the class are 13 years-old.
As 3%2F4 of the 13 years-old group consists of girls, then 13 year-old boys = matrix%281%2C5%2C+1%2F4%2C+of%2C+2%2F5%2C+%22=%22%2C+1%2F10%29
As the same number of buys and girls are in the class, boys and girls are each 1%2F2 of number in class.
Correct answer: Fraction of 14 year-old boys in class: