Direction: In each of the following questions a number series is given. A number is given after the series and then (a), (b), (c), (d) and (e) are given. According to the given series, you have to form a new series which begins with the given number, and then answer the question asked.
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2 3 7 25 121 721 3 (a) (b) (c) (d) (e) Which of the following numbers will come in place of (c) ?
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- 31
- 49
- 45
- 39
- None of these
Correct Option: B
The series is × 2 –1, × 3 – 2, × 4 – 3,.....
The given series is in the below pattern ,
First series :-
First term = 2
Second term = First term × 2 - 1
⇒ Second term = 2 × 2 - 1 = 3
Third term = Second term × 3 - 2
⇒ Third term = 3 × 3 - 2 = 7
similarly , we can calculate the all next terms .
Second series :-
First term = 3
Second term = First term × 2 - 1
⇒ Second term = 3 × 2 - 1 = 5
Third term = Second term × 3 - 2
⇒ Third term = 5 × 3 - 2 = 13
Fourth term = Third term × 4 - 3
⇒ Fourth term = 13 × 4 - 3 = 49
Hence , the place value of ( c ) is 49 .
