What is the correct answer about why the tank does or does not have twice as much water?

Question

Cistern A and Cistern B both have a height of 10 feet. Cistern A has a radius of 10 feet and Cistern B has a radius of 20 feet. Does Cistern B hold twice as much water? Why or why not?

I solved the first part like this. I'm right?

now I have doubts in part two. Is it because of the ratio of 1 to 4?

Thanks!!

V= VA = A*h             

V= pi*r^2*10

V = 3,140 ft^3      

VB = A*h

V= pi*r^2*h

V= 12,560 ft^3

Answer 1

You are absolutely right.

Cistern B holds four times as much water as cistern A.