You make trips to the grocery store to purchase doughnuts. Every time you go, you take a taxi. The round trip taxi ride costs $7.00 and each doughnut costs $0.50.

Question

a) write a function to describe the cost of any given trip to buy doughnuts.
b) What are the values of your domain?

c) You take the taxi to the store and buy four dozen doughnuts. Represent this situation using function notation and find the total cost.

d) Your dad gave you $30.00 to buy doughnuts for your friends. You brought him back $5.00. How many dozens of doughnuts did you buy?

Answer 1

a) The function to describe the cost of any given trip to buy doughnuts can be represented as:
Cost(x) = (Number of doughnuts * $0.50) + $7.00

b) The domain values for this function would be the number of doughnuts you buy since the cost depends on the number of doughnuts purchased. For this situation, the domain values would be positive integers.

c) Using function notation, we can represent the situation as:
Cost(4) = (4 dozen * 12 doughnuts/dozen * $0.50) + $7.00
Cost(4) = $24.00 + $7.00
Cost(4) = $31.00
The total cost for buying four dozen doughnuts is $31.00.

d) Let's assume the number of dozens of doughnuts bought is represented by the variable "d".
We have the equation: (d * 12 * $0.50) + $7.00 = $30.00 - $5.00
(d * 6) + $7.00 = $25.00
(d * 6) = $25.00 - $7.00
(d * 6) = $18.00
d = $18.00 / 6
d = 3
So, you bought 3 dozens of doughnuts.