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CAT 2022 Slot 1 Paper

Question : 47 of 66

Marks: +1, -0

Solution:

It is given,

S_n=2 n^2+n

S_{n-1}=2(n-1)^2+(n-1)

S_{n-1}=2 n^2-3 n+1

T_n=S_n-S_{n-1}=2 n^2+n-2 n^2+3 n-1=4 n-1

T_n=4 n-1

The terms are

3,7,11,15,19,23,27,\ldots

27 is the first term in the series divisible by 9 .

27 is the 7 th term.

Therefore, the least possible value of

n

is 7 .

The answer is option C.

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