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If the sum of the first 2n terms of the ...

If the sum of the first `2n` terms of the A.P. 2, 5, 8, ..., is equal to the sum of the first `n` terms of A.P. 57, 59, 61, ..., then `n` equals

A

10

B

12

C

11

D

13

Text Solution

Verified by Experts

The correct Answer is:
C
According to given condition,
`rArr (2n)/(2) [2 xx 2 + (2n -1) xx 3] = (n)/(2) [2 xx 57 + (n -1) xx 2]`
`rArr (4 + 6n - 3) = (1)/(2) (114 + 2n -2)`
`rArr 6n += 57 + n -1 rArr 5n = 55`
`:. N = 11`
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