Question 1174352
y=kx^2
10=k*5^2
k=10/25 or 0.4
so y=0.4*20^2=160; when x goes from 5 to 20, it increases 4 fold; y will increase 16 fold, from 10 to 160
40=0.4*x^2
100=x^2
x=10
When y increases 4 fold, x increases 2 fold.