Question

If 40% of a school are boys, and 40% of students have blond hair, and there are three times as much of girl as boys to have blond hair. What is the percentage of the class is blonde hair boys?

Answer 1

10 % of the student are blonde hair.

Explanation:

Let number of students be x

40% are boys =
`(2)/(5) x`

so number of girls are = x -
`(2)/(5) x`

=
`(3)/(5) x`

Number of total students which have blond hair = 40 % of x

=
`(2)/(5) x`

number of blonde girls = 3 times number of blonde boys

Let number of blonde boys be y

then number of blonde girls = 3 y [ according to question ]

total blonde = y+3y = 4y

4y = 40% of x [ given]

4y =
`(2)/(5) x`

y =
`(1)/(10) x`

% of blonde hair boys =
`(blonde boys )/(total)X100`

=
`((x/10 )/(x)X100`

= 10 %