Question

Nevaeh uses a gift card to buy a cup of coffee every morning. The table shows the amount of money left on the card, y, as a function of the number of cups of coffee she buys, z.
Find and describe the rate of change of the function.
The rate of change is
It represents
2
19
in the amount on the gift card for every cup Nevaeh purchases. ?
5
10
7
4
X
X
7
8
9X
4
5
6
1
2
3
0
(-)
Number of Cups of Coffee, z
Amount of Money Left on Card ($). y

Answer 1

Rate of change = −2 dollars per cup.

Explanation: Each time z increases by 1 (one more cup), y decreases by 2. So the gift card balance goes down $2 for every cup Nevaeh buys. (From the table y = 19 − 2z, the initial balance is $19 at z = 0.)