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JAMB Mathematics 1978 Question 15

Question 15

Commercial Arithmetic

Father reduced the quantity of food bought for the family by 10% when he found that the cost of living had increased by 15%. Thus the fractional increase in the family food bill is now

  1. A.1/12
  2. B.6/35
  3. C.19/300
  4. D.7/200
  5. E.5/100
Show the answer and explanation

Answer: D (7/200)

Explanation

New bill = 90% of the quantity at 115% of the price = 0.9 × 1.15 = 1.035 of the old bill. The increase is 0.035 = 7/200.