JAMB Mathematics 2020 Objective — Question 12
Question 12 of 40 from the Joint Admissions and Matriculation Board (JAMB) Mathematics 2020 Objective paper, with the correct answer and a full explanation.
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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.
- A. 6
- B. 3Correct
- C. 2
- D. 3/4
Explanation
T7=a+6d, T3=a+2d. Since T7=2T3: a+6d=2a+4d, so a=2d. S4=4a+6d=14d (substituting a=2d). Since S4=42: 14d=42, d=3.
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