If the height of the right circular cone is increased by 200% and the radius of the base is reduced by 50%. Then, the change in the volume of cone is?

From the formula the net change in volume is given as [x + y + z + (xy + yz + zx)/100 + xyz/(100)² ] %
Here, x = 200, y = z = -50 (-ve sign for decrease)
= [ 200 + (-50) + (-50) + (200) x (-50) + (-50) x (-50) + (-50) x (200)/100 + (200) x (-50) x (-50)/(100)² ] %
= 100 + (-10000 + 2500 - 10000)/100 + 500000/100 x 100 ] %
= [ 100 + (-17500)/100 + 50]%
= (150 - 175)% = -25% (-ve sign implies for a decrease )
So, the volume is decreased by 25%.