Which term of the series 5,10, 20, 40,……………….is 1280 ?
A. 10th
B. 9th
C. 8th
D. None of these
Answer & Solution
Answer: Option B
Solution:
Clearly, 5 × 2 = 10, 10 × 2 =20, 20 × 2 = 40,………………………..
So, the series is G.P. in which a = 5 and r = 2.
Let 1280 be the nth term of the series.
Then, 5 × 2n – 1= 1280 ⇔2n – 1= 256 = 28 ⇔ n – 1 = 8 ⇔ n = 9
Also Read:
- 1, 9, 25, 49, ?, 121.
- 4, 7, 12, 19, 28, ?
- 6, 11, 21, 36, 56, ?
- 10, 100, 200, 310, ?
- 8, 28, 116, 584, ?
- 3, 7, 23, 95, ?
- 7, 26, 63, 124, 215, 342, ?
- 165, 195, 255, 285, 345, ?
- 34, 45, 56, 67, ……. What number should come next?
- Find out the wrong number. 150, 450, 750, 1060,1350,1650,1950
