Find the sum of last ten terms


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


For finding, the sum of last ten terms, we write the given AP in reverse order.

i.e., 126,124,122… 12,10,8

Here, first term (a) = 126, common difference, (d) = 124-126=-2

$\therefore \quad S_{10}=\frac{10}{2}[2 a+(10-1) d] \quad\left[\because S_{n}=\frac{n}{2}[2 a+(n-1) d]\right]$



$=5 \times 234=1170$


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