SOLUTION: Given that y directly with the square of x, and y=10 when x=5, find: a) y when x=20 b)x when y=40

Algebra ->  Rational-functions -> SOLUTION: Given that y directly with the square of x, and y=10 when x=5, find: a) y when x=20 b)x when y=40      Log On


   

Question 1174352: Given that y directly with the square of x, and y=10 when x=5, find:
a) y when x=20
b)x when y=40
Answer by Boreal(15235) About Me  (Show Source):
You can put this solution on YOUR website!
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.