Question

Find the sum of first 20 terms of AP -6,0,6.....

Answer 1

Step-by-step explanation:

Given AP is: - 6, 0, 6,....

Here

First term a = - 6

Common Difference d = 6

Number of terms n = 20

We need to find: $S_{20}$

$\because$Sum of n terms of an AP is given as:

$S_{n}= \frac{n}{2}\{2a+(n-1)d \} \\</p><p>\therefore S_{20}= \frac{20}{2}\{2(-6)+(20-1)\times 6\}\\</p><p>\therefore S_{20}= 10\{-12+19\times 6\}\\\therefore S_{20}= 10\{-12+114\}\\\therefore S_{20}= 10\{102\}\\\therefore S_{20}= 1020$