Question

Find the sum of the first 25 terms of the arithmetic sequence.
$a_1=100\:and\:a_{25}=220$

Answer 1

Answer:

Step-by-step explanation:

$\frac{n}{2}*(a+l)=\frac{25}{2}*(100+220)\\\\=\frac{25}{2}*320=\frac{25*320}{2}\\\\=25*160=4000$