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Logical Reasoning
Number Series
In an AP if a = 1, an = 20 and Sn = 399, then n is
(A) 19 (B) 21
(C) 38 (D) 42
Read Solution (Total 2)
-
- sn=n/2*(a+an)
n=38 - 10 years agoHelpfull: Yes(3) No(1)
- sn = 1/2 (a+an)*n
Hence n=38 - 9 years agoHelpfull: Yes(2) No(1)
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