Question

P varies directly with the square of R. When R is 4, P is 56. Find the value of P when R is 6

Answer 1

Hey!
The formula of direct variation is y = kx. So we know that p = kr^2
Hint: after it says varies, it's basically the equal sign. 
so we can set it up
56 = 4^2k
56=16k
now we want k alone so we have to divide 16 on both sides
k=3.5
We can now solve for p like it asks
p = 3.5*6^2
p=126
There's your answer!
Hope this helps!