Question

If the price of the petrol be raised by 20%,then what is the percentage by which a car owner must reduce its consumption so as not to increase his expenditure on petrol. ​

Answer 1

Given :- The price of the petrol be raised by 20%,then what is the percentage by which a car owner must reduce its consumption so as not to increase his expenditure on petrol. ?

Solution :-

To make calculation easy, let us assume that, initial Price of petrol was Rs.10 , and initial consumption was also Rs.10 .

Now, we know that,

→ Price * Consumption = Expenditure .

So,

→ 10 * 10 = Expenditure

→ Expenditure = Rs.100 . (Initial.)

Now, we have given that, Price of Petrol is raised by 20% .

So,

→ New Price of petrol = initial Price + 20% of initial Price.

→ New Price = 10 + 20% of 10

→ New Price = 10 + (20 * 10/100)

→ New Price = 10 + 2

→ New Price = Rs.12

Also,

→ New expenditure = Old expenditure = Rs.100 .

Therefore,

→ New Price * New Consumption = New Expenditure .

→ 12 * New Consumption = 100

→ New Consumption = (100/12)

→ New Consumption = Rs. (25/3) .

Hence,

→ New Consumption is reduced by = Old consumption -

New Consumption = 10 - (25/3) = (30 - 25/3) = Rs.(5/3) .

→ Required % reduce = (Reduced value in Rs. * 100 ) / (initial Price) = {(5/3) * 100} / 10 = (5 * 100) / (3 * 10) = (50/3) ≈ 16.67% . (Ans.)

∴ car owner must reduce its consumption by 16.67% so as not to increase his expenditure on petrol.