If the radius of a right circular cylinder is decreased by 10%, and the height is increased by 20%, then the percentage increase/decrease in its volume is:

decrease quadrilateral by in 2.8%

We know that,

Volume of cylinder = π r² h

We have,

If a radius is r and decreased bt 10% then it becomes = 90% of r

Also,h increased by 20%  then height will be = 120% of h 

Volume = π × 120% of h  × 90% of r = 0.972πrh

Required percentage = (πrh - 0.972πrh) × \(\frac{1}{ πrh  }\) × 100 = 2.8%