Multiple choice general knowledge math & puzzles

if price of petrol increased by 25% and priya wants to spend additional 15% on petrol. What % of petrol quantity will she reduce?

  1. 10%

  2. 12%

  3. 8%

  4. 7%
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Let original price = P, quantity = Q. New price = 1.25P. New spend = 1.15PQ (15% more). New quantity = (1.15PQ)/(1.25P) = 0.92Q. So quantity reduces by 8%. Formula: (1+%spend)/(1+%price) - 1 gives the % change in quantity. (1.15/1.25) - 1 = 0.92 - 1 = -0.08 = -8%.

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