Question

The price (per litre) of petrol increases by 50%. By what percent should its consumption be reduced such that the expenditure on it increases by 23% only?

• A. 18%
• B. 81%
• C. 21%
• D. 82%

Answer 1

Answer:

A. 18%

Let initial price = 100 and initial consumption = 100 litres

Initial expenditure

$100 \times 100 = 10000$
New price (increase by 50%)

$100 \rightarrow 150$
New expenditure (increase by 23%)

$10000 \rightarrow 12300$
Find new consumption

$150 \times \text{new consumption} = 12300$
$\text{new consumption} = \frac{12300}{150} = 82$
Reduction in consumption

$100 - 82 = 18$

Percentage reduction

$\frac{18}{100} \times 100 = 18\%$