Go To Your Study Dashboard

Get Answers to all your Questions

header-bg

Find the sum of last ten terms of the AP: 8, 10, 12, __________ , 126.

Answers (1)

$\text{The given AP is } 8, 10, \ldots, 126 \\ \text{AP from last is } 126, 124, \ldots, 10, 8 \\ a = 126 \\ d = 124 - 126 = -2$

The sum of 10 terms from last-
$S_{n}=\frac{n}{2}[2 a+(n-1) d] \\$
$\text{Put } n=10$
$\begin{aligned} S_{10} &= \frac{10}{2}[2 \times 126 + (10 - 1) \times (-2)] \\ &= 5[252 + 9 \times (-2)] \\ &= 5[252 - 18] \\ S_{10} &= 5 \times 234 = 1170 \\ S_{10} &= 1170 \end{aligned}$

Posted by

infoexpert21

View full answer

Similar Questions

Latest Question