The petrol price shot up by 10% as a result of the hike in crude oil prices. The price of petrol before the hike was ₹ 90 per litre. A person travels 2200 km every month and his car gives a mileage of 16 km per litre. By how many km. should he reduce his travel if he wants to maintain his expenditure at the previous level?

The correct answer is 200 km.

Let's solve the problem step-by-step to understand how to maintain the expenditure at the previous level after the price hike.

Step 1: Understand the initial scenario
Initial price of petrol = ₹ 90 per litre.
Monthly distance travelled = 2200 km.
Mileage of the car = 16 km per litre.

Step 2: Calculate the initial quantity of petrol consumed and monthly expenditure
The quantity of petrol used per month before the hike is given by:

$\text{Initial Petrol Consumed}=\frac{2200}{16}=137.5\text{ litres}$

Initial monthly expenditure on petrol:

$\text{Initial Expenditure}=137.5\times 90=\text{₹ }12375$

Step 3: Calculate the new price of petrol after the 10% hike
Increase in petrol price = 10% of ₹ 90:

$\text{Increase}=\frac{10}{100}\times 90=\text{₹ }9$

New price of petrol per litre:

$\text{New Price}=90+9=\text{₹ }99\text{ per litre}$

Step 4: Find the allowed petrol consumption to keep expenditure constant
To maintain the expenditure at ₹ 12375 with the new price of ₹ 99 per litre, the maximum petrol he can afford is:

$\text{New Petrol Allowed}=\frac{12375}{99}=125\text{ litres}$

Step 5: Calculate the new distance he can travel
Distance covered with 125 litres of petrol:

$\text{New Distance}=125\times 16=2000\text{ km}$

Step 6: Calculate the reduction in distance
The reduction in travel required is:

$\text{Reduction in distance}=2200-2000=200\text{ km}$

Thus, he should reduce his travel by 200 km to maintain his expenditure at the previous level.