5 would be the answer to it
In the science class,
there are 3 girls and 1 boy (grade 7)
and 5 girls and 5 boys (grade 8)
There is a total of 14 pupils being 8 girls and 6 boys
The probability of choosing a boy will be

Which can be simplified into

by
dividing 2 from the numerator as well as the denominator.
The first one is finding the square root of things I believe and I'm not sure about the second one sorry
Because you are not multiplying 250 by a number larger than 1. If you multiply 250 by a number larger than 1 the product will be larger than 250. If you multiply 250 by a number less than 1 the product will be less than 250.
Hope that helps!