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In "Number Series" question, a number series is given with one term missing. Choose the correct alternative that will same pattern and fill in the blank spaces

In following question, a number series is given with one term missing. Choose correct alternative

4, 8, 28, 80, 244, x

Option:
A. 628
B. 728
C. 656
D. 756
Answer: B . 728

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

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