Question

A community organizes a phone tree in order to alert each family of emergencies. In the first stage, one person calls five families. In the second stage, each of the five families calls another five families, and so on. How many stages need to be reached before 600 families or more have been called?

Answer 1

Basically you are multiplying each thing by 5
1   stage 1
5  stage 2
25  stage 3
125  stage 4
625  stage 5
3125  stage 6

Answer 2

1 + 5 + 25 + 125 + 625

Up to stage 3, 125, a total of 1 + 5 + 125 = 131 families had been called which is less than 600 families..
In stage 4, 625 families are called, which makes a total of over 600 families called.

Answer: 4 stages.