In a school, the number of girls exceeds in its third part, the number of boys.
Is it correct that, boys are $\frac{2}{5}$ of total students?
$g =$ girls
$b = b$
$g = b + \frac{1}{3}g$
$\frac{2}{3}g = b$ and $\frac{3}{2}b = g$
The total amount of students, in function of girls are:
$\frac{2}{3}g + g = \frac{5}{3}g$
The total amount of students, in function of boys are:
$\frac{3}{2}b + b = \frac{5}{2}b$
Well up here, I have all the quantities.
But none in terms of $\frac {2} {5}$, then what should I do?
As you said:
“The total amount of students, in function of boys are:
$\frac{3}{2}b + b = \frac{5}{2}b$ ”
Let $T$ be the total number of students.
Then your words mean $$T= \frac{3}{2}b + b = \frac{5}{2}b$$
So we have $$T=\frac{5}{2}b$$ $$b=\frac{2}{5}T$$
The boys are $\frac{2}{5}$ of the total.