# Math

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...

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1. boys : girls = 5:2
So, if there are 5x boys, there are 2x girls
5x+2x = 42
x = 6

Now what do you say?

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2. So basically the number of boys is 6?
And so is girls??

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3. NO!
I solved for the value of x.
Now go back and read what I said about the number of girls and boys.

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oobleck
4. 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?

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5. 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.

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oobleck

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