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WAEC Mathematics 1994 Question 10

Question 10

Progressions

The sum of the 1st and 2nd terms of an A.P. is 4 and the 10th term is 19. Find the sum of the 5th and 6th terms.

  1. A.11
  2. B.20
  3. C.21
  4. D.22
  5. E.24
Show the answer and explanation

Answer: B (20)

Explanation

a + (a + d) = 4 and a + 9d = 19 give d = 2 and a = 1. Then T5 + T6 = (1 + 8) + (1 + 10) = 20.