First slide

Arithmetic progression

Question

If the sum of the series 2, 5, 8, 11, ………. n terms is 60100, then find the value of n.

Moderate

A

100
B

200
C

300
D

400

Solution

Here first term is a=2 and common difference d=3.
Hence sum of n terms of A.P. is (n/2)(4+3(n-1))=60100
$\begin{array}{l} \Rightarrow 3 n^{2} + n - 120200 = 0 \\ \Rightarrow (n - 200) (3 n + 601) = 0 \Rightarrow n = 200 \end{array}$

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