4. A bike rental company rented out 8 bikes in its first month. The company increased the number of bikes it rented each month by 2%. What was the approximate total number of bikes the company will rent out for the first 9 months?

50

59

68

78

This is a geometric sequence:

First month: 8

Second month: 8 * 1.02

Third month: 8*1.02^2

Fourth month 8 * 1.02^3

...

nth month: 8 * 1.02 ^ (n-1)

Sum of the first 9 terms (months) = a[1 - r^n] / (1 - r) = 8 * [1 - 1.02^9] / (1 - 1.02) = 78.04

Answer: approximately 78 bikes.