If the price of petrol increases from Rs. 90/l to Rs. 110/l, by what percentage does a person have to decrease his consumption so that his expenditure on petrol remains the same (approximate to two decimals)?

Correct option is C

Given:
Initial price of petrol, P₁ = 90 Rs./l
New price of petrol, P₂ = 110 Rs./l
Expenditure remains the same
Formula Used:
Since expenditure remains the same,
P₁ × C₁ = P₂ × C₂
Percentage decrease in consumption = $$\left(\frac{C_1 - C_2}{C_1}\right) \times 100$$​​
Solution:
From the expenditure equality,
90 × C₁ = 110 × C₂
​$$C_2 = \frac{90}{110} \times C_1 = \frac{9}{11} \times C_1$$​​
So, percentage decrease in consumption,
​$$= \left(1 - \frac{9}{11}\right) \times 100 = \frac{2}{11} \times 100 \approx 18.18\%$$​​