Chapter 14 - Sequences, Series, and the Binomial Theorem - 14.2 Arithmetic Sequences and Series - 14.2 Exercise Set: 36

$S_{400}=80200$

Work Step by Step

The first n term of an arithmetic sequence can be calculated as: $S_n=\frac{n}{2}(a_1+a_n)$ We have to find the sum of the first 400 natural numbers. $a_1=1$ $a_{400}=400$ Therefore we can substitute in the formula of the sum, and we get: $S_{400}=\frac{400}{2}(1+400))=200\times401=80200$

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