If the radius of the base of a right circular cylinder is increased by 20% and the height is decreased by 30%, then what is the percentage increase/decrease in the volume?

Solution (By Examveda Team)

$$\eqalign{ & V = \frac{1}{3}\pi {r^2}h \cr & r \to 20\% \to \frac{{ + 1}}{5} \cr & h \to 30\% \to \frac{{ - 3}}{{10}} \cr & {r^2} \Rightarrow {5^2}:{6^2} \cr & h \Rightarrow 10:7 \cr & V \Rightarrow 250:252 \cr & {\text{Increase}} = 2 \cr & {\text{Increase }}\% = \frac{2}{{250}} \times 100 = 0.8\% \cr} $$