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?
<pre>The other person is WRONG!
{{{2/5}}} of the class are 13 years-old.
As {{{3/4}}} of the 13 years-old group consists of girls, then 13 year-old boys = {{{matrix(1,5, 1/4, of, 2/5, "=", 1/10)}}} 
As the same number of buys and girls are in the class, boys and girls are each {{{1/2}}} of number in class.
Correct answer: Fraction of 14 year-old boys in class: {{{highlight_green(matrix(1,7, 1/2 - 1/10, "or", 5/10 - 1/10, "=", 4/10, "or", 2/5))}}}