Answer:
12
Explanation:
Let's create a table
2 : 5 is the same as 2x : 5x because you multiply both sides in 2:5 by x
If the ratio is 2x : 5x, what is the total?
2x + 5x = 7x
The total is 7x
However, we are given that there are 42 students
So, 7x = 42
x = 6
As we said earlier, boys = 2x
We know that x = 6, so 2x must equal to 12
There are 12 boys.
Hope this helps :)
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