The price (per litre) of petrol increases by 75%. By what approximate percent should its consumption be reduced such that the expenditure on it increases by 33% only?

Question

PYQPulse · Accepted Answer

24%

PYQPulse · Answer

Explanation: Let initial price be P and consumption C; initial expenditure = P×C. New price = 1.75P; new expenditure must be 1.33×(P×C). New consumption C′ satisfies 1.75P × C′ = 1.33PC → C′ = (1.33/1.75)C = 0.76C. Reduction = 1 − 0.76 = 0.24, i.e., 24%.

The price (per litre) of petrol increases by 75%. By what approximate percent should its consumption be reduced such that the expenditure on it increases by 33% only?

Answer: A. 24%

Explanation