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Question

Mathematics Question on Sum of First n Terms of an AP

If Sn=3+7+11....S_n=3+7+11.... upto nn terms and 40<6n(n+1)k=1nSk<4540<\frac {6}{n(n+1)}\displaystyle\sum_{k=1}^n S_k<45. Then nn is

A

9

B

10

C

11

D

12

Answer

9

Explanation

Solution

The correct option is (A): 9