Given the series: 4, 7, 12, 21, 38, .. What is sum of seventh and ninth term?

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24 Jun 2020 Series

Given the series:
4, 7, 12, 21, 38, ..
What is sum of seventh and ninth term?

OPtion

1) 810
2) 658
3) 626
4) 536
5) 696
6) 691
7) 698
8) 502
9) 582
10) None of these

Solution

Series is formed by adding 2^n+1 in previous number
So
4 + 2^1+1 = 7
7 + 2^2+1 = 12
12 + 2^3+1 = 21
21 + 2^4+1 = 38
38 + 2^5+1 = 71
71 + 2^6+1 = 136
136 + 2^7+1 = 265
265 + 2^8+1 = 522

Sum of 522 + 136 = 658

Correct Option: 2 Best Solution (0)