Question

A random object hit the top of a mountain and caused several boulders to fall down the mountain. Scientists were able to measure the speed of the boulders. The distance (in feet) that the boulder traveled down the mountain each second was given by the arithmetic sequence: 3, 5, 7, 9, . . . Find the total distance the boulder traveled in 9 seconds.​

Answer 1

Explanation:

The hard way to do this (no calculator) is

a = 3

n = 9

d = 2

Total = (a + a + (n-1)*d

Total = 2*3 + (9 - 1)*2

Total = 6 + 8*2

Total = 22 feet in 9 seconds.

Seems small.