# Which is the Term of 1280 in Series 5, 10, 20, 40, ……………?

- 7th
- 10th
- 9th
- None of these

**Answer: (3) 9th**

**Explanation:-
**5, 10, 20, 40, ……………………

Then, 5 x 2 = 10, 10 x 2 = 20, 20 x 2 = 40 …………….

Then, a = 5 and r = 2

Therefore, the given series is G. P. (Geometric Progression),

Let the number of terms be n.

Then, 5 x 2^{n – 1} = 1280

2^{n – 1} = 1280/5

2^{n – 1} = 256

2^{n – 1} = 2^{8}

n – 1 = 8

n = 8 + 1

n = 9

Then, the 9th term is 1280.

Hence, the answer is (3) 9th.