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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

1, ?, 5, 10, 20, 40, 80

Options:

A. 1       B. 2       C. 2.5       D. 4       E. None of these

Answer:      D . 4

Justification:      

Next number is sum of all previous numbers.

1st Term : 1

2nd Term: 4

3rd Term: 1+4 =5

4th Term: 1+4+5= 10

5th Term: 1+4+5+5=20 and so on....

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