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JAMB Mathematics 1982 Question 21

Question 21

Number Bases

The currency used in a country is called 'Matimalik' (M) and is of base seven. A lady in that country bought 4 bags of rice at M 56 per bag and 3 tins of milk at M 4 per tin. What is the total cost of the items she bought?

  1. A.M246(7)
  2. B.M242(7)
  3. C.M236(7)
  4. D.M341(7)
  5. E.M338(7)
Show the answer and explanation

Answer: D (M341(7))

Explanation

56₇ = 41 in base ten, so the rice costs 4 × 41 = 164 and the milk 3 × 4 = 12, total 176. In base seven 176 = 3 × 49 + 4 × 7 + 1 = 341₇.