Q. 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?

Explanation : 

1. Calculate the new price of petrol after a 10% hike:
New price = ₹90 × (1 + 10/100) = ₹90 × 1.10 = ₹99 per litre.

2. Find his original monthly fuel consumption:
Distance = 2200 km, Mileage = 16 km/litre
Fuel used = 2200 ÷ 16 = 137.5 litres.

3. Compute his original monthly expenditure:
Expenditure = 137.5 litres × ₹90 = ₹12 375.

4. Determine how much fuel he can buy at the new price to keep the same ₹12 375 spending:
Let allowed fuel = L litres.
L × ₹99 = ₹12 375
L = 12 375 ÷ 99 = 125 litres.

5. Find the distance he can travel with 125 litres at 16 km/l:
Distance = 125 × 16 = 2000 km.

6. Calculate the reduction in travel to maintain the same expenditure:
Reduction = Original distance – New distance
= 2200 km – 2000 km
= 200 km.

Therefore, he must cut his monthly travel by 200 km.