Question

if the radius of a cone is multiplied by 8,how many times larger ids the new volume?

Answer 1

You did not mention anything about the height so I will assume the height stays the same.

original volume = (1/3)πr^2h
new volume = (1/3)π(8r)^2h = (64/3)πr^2h

so the volume has increased 64 times the original.