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In an A.P., if a = 1 , a(n) = 20 and S(n...

In an A.P., if a = 1 , `a_(n) = 20` and `S_(n) = 399`, then n = ……..

A

19

B

21

C

38

D

42

Text Solution

Verified by Experts

The correct Answer is:
C
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