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JAMB Mathematics 2005 Question 19

Question 19

Progressions

If the 7th term of an AP is twice the third term and the sum of the first four terms is 42, find the common difference.

  1. A.6
  2. B.3
  3. C.2
  4. D.1
Show the answer and explanation

Answer: B (3)

Explanation

a + 6d = 2(a + 2d) gives a = 2d. Then 4a + 6d = 42 becomes 14d = 42, so d = 3.