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?
Answer & explanation
Answer: (b) 200 km
With a fixed budget, the distance he can drive is inversely proportional to the petrol price. A 10% price rise brings the distance down to 100/110 of 2200 km, i.e. 2000 km, so he must travel 200 km less.
- New price = ₹90 × 1.1 = ₹99 per litre.
- Petrol used now: 2200 ÷ 16 = 137.5 litres, costing 137.5 × 90 = ₹12,375.
- At ₹99 a litre, ₹12,375 buys 12,375 ÷ 99 = 125 litres, enough for 125 × 16 = 2000 km.
- Reduction = 2200 − 2000 = 200 km.
- Check (faster route): distance falls in the ratio 100 : 110, so 2200 × 100/110 = 2000 km; the mileage figure is not even needed.
Remember · Fixed spending: quantity varies inversely with price. A p% price rise cuts quantity by p/(100 + p) — here 10/110 = 1/11.
Question and answer: UPSC's official GS Paper II (2025, Series A) — paper ↗ · answer key ↗. Explanation: Minimalist IAS, checked 30 Sept 2026 (how we verify). ·