The sum of first 20 odd natural numbers isA. 100B. 210C. 400D. 420 – InterviewSolution

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1.	The sum of first 20 odd natural numbers isA. 100B. 210C. 400D. 420
Answer» Correct Answer - C `S_(20) = 1+3 +5 +7 +…` up to 20 terms. Here a = 1, d = 2. So, `T_(20) = (a+19d) = (1+19 xx 2) = 358 = l.` `therefore S_(20)= (n)/(2)(a+l) = (20)/(2) (1+39) = 400`

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