Home > PC3 > Chapter 12 > Lesson 12.1.1 > Problem12-10

12-10.

Evaluate each the following sums.

1. $3 + 6 + 9 + … + 90$

Add the first and last terms.
Divide by $2$.
Multiply by the number of terms.

1. $20 + 22 + 24 + … + 100$

How many terms are there?

$41$

1. $\displaystyle \sum _ { n = 1 } ^ { 41 } ( 2 n + 18 )$

Add the first and last terms.
Divide by $2$.
Multiply by the number of terms.

1. $\displaystyle \sum _ { k = 8 } ^ { 53 } ( 5 k - 3 )$

How many terms are there? That is, if the sum started with $k = 1$, what would it end with?

$46$