Question

A parking garage charges $5.50 to park for 4 hours and $7.75 to park for 7 hours. If the cost is a linear function of the number of hours parked, what is the cost to park for 3 hours?

Answer 1

Answer:

see bottom

Step-by-step explanation:

y=mx+b

m=slope

b=yint

two points

cost=y

(4,5.5) and (7,7.75)

slope=(y2-y1)/(x2-x1)

slope=(7.75-5.5)/(7-4)=2.25/3=0.75

y=0.75x+b

find b

(4,5.5)

x=4

y=5.5

5.5=0.75(4)+b

5.5=3+b

minus 3 fromboth sides

2.5=b

y=0.75x+2.5

3 hours

y=0.75(3)+2.5

y=2.25+2.5

y=4.75

answer is D

Answer 2

Given:
hours     parking charge
4                 5.50
7                 7.75

7 - 4 = 3 hours
7.75 - 5.50 = 2.25

2.25 / 3 = 0.75

0.75 is the change in amount for every hour spent. It is the variable unit rate

4 hours is 5.50.

Cost of parking for 3 hours is: 5.50 - 0.75 = 4.75

0.75 x 4 hours = 3 
5.50 - 3 = 2.5 fixed charge.

total parking charge:  y = 2.50 + 0.75x