Question

At the beginning of the year, Zachary had $40 in savings and saved an additional $20 each week thereafter. Isaac started the year with $85 and saved $11 every week. Let Z(t) represent the amount of money Zachary has saved tt weeks after the beginning of the year and let I(t) represent the amount of money Isaac has saved tt weeks after the beginning of the year. Write the equation for each function and determine the interval of time when Zachary has more in savings than Isaac.

Answer 1

Zachary function:

Z(t) = 40 + 20t

Isaac function:

I(t) = 85 + 11t

Graph each function to see the interval of time when one person has more money than the other.