### Home > A2C > Chapter 12 > Lesson 12.1.3 > Problem 12-49

12-49.

Find the sum of the arithmetic series below. Homework Help ✎

5 + 10 + 15 + 20 + … + 400

3 + 8 + 13 + 18 + … + 398

80 + 74 + 68 + 62 + … + 14

Find the sequence that describes the series.

*t*(*n*) = 5*n*

Find which term is 400.

(400) = 5*n*

80 = *n*

Find the sum using the formula from the Math Notes box.

16200

See part (a).

16040

See part (a).