Answer:
A 36.
Explanation:
If x is the number of boys then √x is the number of girls.
x + √x = 42
√x = 42 - x
Squaring both sides:
x = (42 - x)^2
1764 - 84x + x^2 - x = 0
x^2 - 85x + 1764 = 0
(x - 36)(x - 49) = 0
x = number of boys = 49 or 36.
But the total number = 42 so there must be 36 boys. Also √36 = 6 so the answer is 36 boys.