##### What is the answer to this problem?

label Programming
account_circle Unassigned
schedule 1 Day
account_balance_wallet \$5

Find the sum of the first 25 terms of the arithmetic sequence: 7,19,31,43,...

May 25th, 2015

Sum of n terms of an AP is given by

Here,

n=25

a1=7

d=19-7=12

$S_n=\frac{n}{2}[ 2a_1 + (n-1)d] \\\Rightarrow S_n=\frac{25}{2}[ 2 \times 7 + (25-1)12] \\\Rightarrow S_{25}=\frac{25}{2}[ 14 + 24 \times 12] \\\Rightarrow S_{25}=\frac{25}{2}[ 14 + 288] \\\Rightarrow S_{25}=\frac{25 \times 302}{2}=7550 \\\Rightarrow \boxed{S_{25}=7550}$

=======================================================================

Ask back if you have any doubt. I am here.

May 25th, 2015

...
May 25th, 2015
...
May 25th, 2015
Jun 26th, 2017
check_circle