Asked by student #1

A class has 42 pupils. The ratio of the number of boys to the number of girls is 5 : 2. Find the number of boys in the class.

My understanding is that in order to find the number of boys, you need to find BOTH genders first, and so I could only get up to the number of GIRLS, which I did: 42 divided by 2 = 21
42 divided by 5 = 8.4
But now I'm stuck...
Please help and see if my understanding is correct...
Answered by oobleck
boys : girls = 5:2
So, if there are 5x boys, there are 2x girls
5x+2x = 42
x = 6

Now what do you say?
Answered by student #1
So basically the number of boys is 6?
And so is girls??
Answered by oobleck
NO!
I solved for the value of x.
Now go back and read what I said about the number of girls and boys.
Answered by student #1
Ohhhh I get it

So 5x = 5 x 6 = 30 (BOYS)
And 2x = 2 x 6 = 12 (GIRLS)

So the number of boys is 30 yes?
Answered by oobleck
that's better.

Consider a "group" of students to be 5 boys and 2 girls.
x is the number of such groups in the class.
Answered by 30
5×5×5×1030