Find the sum of first $16$ terms of the AP: $10,\ 6,\ 2\ .......$


Given: AP: $10,\ 6,\ 2\ .......$

To do: To find the sum of first $16$ terms of the A.P.

Solution:

$a=10,\ n=16,\ d=6-10=-4$

We know that

$S_n=\frac{n}{2}[2a+( n-1)d]$

$S_{16}=\frac{16}{2}[2\times 10+(16-1)( -4)]$

$\Rightarrow S_{16}=8[20+15( -4)]$

$\Rightarrow S_{16}=8\times ( -40)$

$\Rightarrow S_{16}=-320$

Thus, the sum of first $16$ terms of the given A.P. is $-320$.


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Updated on: 10-Oct-2022

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