In following number series, two terms have been put within brackets. Choose the appropriate option
4, 8, 28, 80, 244, x
Option:
A. 628
B. 728
C. 656
D. 756
Answer: B . 728
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Justification:
The patter is alternate 3^n+1 and 3^n-1.
So following above formula we get:
3^1 + 1 =3+1=4
3^2 - 1 =9-1=8
3^3 + 1 =27+1=28
3^4 - 1 =81-1=80
3^5 + 1 =243+1=244
So last no 3^6-1=729-1=728
