Published by:
CGP EDU Academic Team
Published on: August 14, 2026
The sum of an infinite geometric series is 2 and the sum of the geometric series made from the cubes of this infinite series is 24. Then the series is -
A
3 + 
– 
+ 
….
– + ….
B
3 + 
+ 
+ 
+ ….
+ + + ….
C
3 – 
+ 
– 
+ ….
+ – + ….
D
None of these
Text Solution
Verified by ExpertsThe correct answer is:
C
Let first term = a, common ratio = r,
Where –1 < r < 1
Then, 
= 2 and 
= 24
∴ 
= 
i.e. 1 – 2r + r 2 = 3 (1 + r + r 2 )
or 2r 2 + 5r + 2 = 0.
∴ r = –2 or – 
.
As –1 < r < 1 ∴ we have r = – 
Putting this value of r, we get a = 3,
∴ The series is 3 – 
+ 
– 
+ ……
Hence is the correct answer.
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