Question

The price of petrol goes up by 10%. By how much percent must a motorist reduce the compsumption of petrol so that the expenditure on it remains unchanged?

Answer 1

Let the initial price of petrol be Rs. x

Then, price after increase of 10 % = 100 + (100*10)/100

= 100 + 10

Price after increase of 10 % = Rs. 110

Now,

Reduction in consumption of petrol in percent = [{(110 - 100)}*100]/110

⇒ (10*100)/110

⇒ 100/11

⇒ 9.09 %

So, the motorists have to reduce the consumption of petrol by 9.09 %, so that the expenditure on it remains unchanged.