WAEC Further Mathematics 2025 Objective — Question 9
Question 9 of 40 from the West African Examinations Council (WAEC) Further Mathematics 2025 Objective paper, with the correct answer and a full explanation.
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The third and seventh terms of an exponential sequence (G.P.) are 9 and 1/9 respectively. Find the first term.
- A. 81Correct
- B. 27
- C. 9
- D. 1/3
Explanation
U3=ar²=9 and U7=ar⁶=1/9. Dividing, r⁴=1/81, so r=1/3. Then a = 9/r² = 9×9 = 81.
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