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 11% only?

Correct option is B

Given:

Price increase = 50%

Expenditure increase = 11% 

Formula Used:

% Reduction in consumption = $$\frac{x - y}{x} \times 100$$​​

Solution:

Let original price = ₹10 per litre

Let original consumption = 10  litres

Then original expenditure = 10 × 10 = 100

New price = ₹15 per litre

Let new consumption = y  litres

Then new expenditure = 15 × y  = 15y

Now, 

15y  =  100 × 1.11

y = $$\frac{111}{15}$$​​

= 7.4

So, reduction % 

=$$\left(\frac{10 - 7.4}{10}\right) \times 100 = 2.6 \times 10$$​ = 26% 

Alternate Solution: 

Now,  150 - 111 = 39 

in % = $$\frac{39}{150}\times 100 = 26\%$$​​