Y is directly proportional to the square of x. Find percentage increase in value of y when value of x is doubled

Answer 1

y = kx^2

when x is doubled, you have

k(2x)^2 = 4kx^2 = 4y
so, y has grown by 300%

Answer 2

(2x)^2 --> 4Y

4Y is 300% greater than Y.