Question

If it diameter we’re reduced by half it’s volume would be

Answer 1

Well lets work it out.
Diameter = 2 * Radius
Diameter * 1/2 = 1/2 * 2 * Radius
That would mean that the Radius would also be halved.
(1/2 * Radius)^2 * pi * height = volume, and 0.5^2 = 1/4, so its volume is reduced by a fourth