The sum of the first 5 terms of a geometric progression is the same as the sum of the first 7 terms of the same progression. If the sum of the first 9 terms is 24, then the 4th term of the…
Question and options
The sum of the first 5 terms of a geometric progression is the same as the sum of the first 7 terms of the same progression. If the sum of the first 9 terms is 24, then the 4th term of the progression is
- -48
- -24
- 24
- 48
Answer and explanation
Correct answer: B - -24
S5 = S7 means a6 + a7 = ar^5(1+r) = 0, so r = -1. Then S9 = a = 24, and T4 = a r^3 = -24.
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