If p varies directly as q and inversely as square of r, what is the percentage increase in p due to an increase in q by 20% and a decrease in r by 20%?

Explanation

Given p \propto \frac{q}{r^2}. The new value p' \propto \frac{1.2q}{(0.8r)^2} = \frac{1.2}{0.64} \frac{q}{r^2} = 1.875 p. The increase is 1.875 - 1 = 0.875, which is 87.5\%.

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