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In an A.P, 1st term is 1 and the last te...

In an A.P, `1st` term is `1` and the last term is `20`.The sum of all terms is `399`, then `n=….` a)`42` b)`38` c)`21` d)`19`

A

42

B

38

C

21

D

19

Text Solution

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The correct Answer is:
B
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