2021 · Q41
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% ?
Elementary MathematicsPercentages
- A87.5%
- B85%
- C82.5%
- D80%
Explanation
Write p = c·q/r². Increasing q by 20% multiplies it by 1.2; decreasing r by 20% multiplies r² by 0.8² = 0.64. Hence p is multiplied by 1.2/0.64 = 1.875. The percentage increase is 87.5%, option (a).