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UPSC Prelims 2025 CSAT, question 17

Topic: Arithmetic

Q17

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 ?

  1. (a) 180 km
  2. (b) 200 kmCorrect answer
  3. (c) 220 km
  4. (d) 240 km

Solution.

Answer: (b) 200 km

  1. When the petrol price increases by 10%10\% (becomes 1110\frac{11}{10} of the original price), keeping monthly expenditure unchanged requires reducing petrol consumption (and distance travelled) to 1011\frac{10}{11} of the original distance.
  2. With an initial travel distance of 22002200 km, the required reduction is 2200−2200×1011=220011=2002200 - 2200 \times \frac{10}{11} = \frac{2200}{11} = 200 km.

Trap: The initial price (₹90/litre) and mileage (16 km/litre) cancel out when computing the distance reduction for constant expenditure.