### Home > INT3 > Chapter 10 > Lesson 10.3.3 > Problem10-187

10-187.

What is the sum of each series?

1. $11 + 12 + 13 + \ldots + 40$

Find the sequence that describes the series.

$t\left(n\right) = 10 + n$

Find which term is $40$.

$\left(40\right) = 10 + n$
$30 = n$

Find the sum using the formula

$S(k)=\frac{k(t(1)+t(k))}{2}$

$S(30)=\frac{30(11+40)}{2}$

1. $90 + 84 + 78 + \ldots + 24$

See part (a).