Question

A parent increases a child’s monthly allowance by 20% each year. If the allowance is $8 per month now, in about how many years will it take to reach $20 per month? Use the equation 20 = 8(1.2)x to solve the problem. Round to the nearest year.

Answer 1

6 years

A parent increases a child’s monthly allowance by 20% each year. If the allowance is $8 per month now. This is an exponential function, An exponential function is given by:

Let x be the number of years and y be the allowance. The initial allowance is $8, this means at x = 0, y = 8

Since it increases by 20% each year, i.e 100% + 20% = 1 + 0.2 = 1.2. This means that b = 1.2
Therefore:

To find the number of years will it take to reach $20 per month, we substitute y = 20 and find x

x = 6 years to the nearest year