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JAMB Mathematics 1989 Question 15

Question 15

Variation

The cost of a dinner for a group of students is partly constant and partly varies directly as the number of students. If the cost is N74.00 when the number of students is 20, and N96.00 when the number is 30, find the cost when they are 15 students.

  1. A.N68.50
  2. B.N63.00
  3. C.N60.00
  4. D.N52.00
Show the answer and explanation

Answer: B (N63.00)

Explanation

C = a + ks. From 74 = a + 20k and 96 = a + 30k, k = 2.2 and a = 30. For 15 students C = 30 + 2.2 × 15 = N63.