Question

The number of cars (c) in a parking lot increases when the parking fee (f) decreases. Write the correct equation for this scenario, and solve for the number of cars when the fee is $6. Fee Cars 20 15 30 10

Answer 1

Data:

Fee   Cars
20     15
30     10

Given that you have only two set of data, you can only assume a linear model.

To find the linear model (equation) that predict the number of cars (x) as a functionn of the parking fee (f) you follow, using only two set of data, follow this procedure:

1) Find the slope, m

m = [10 - 15] / [30 - 20] = - 5 / 10 = - 0.5

2) Use the slope-point equation

y - y1 = m (x - x1)

=> y - 10 = - 0.5 (x - 30)

=> y - 10 = - 0.5x + 15

=> y = - 0.5x + 15 + 10

=> y = - 0.5x + 25

or c = - 0.5 f + 25  <-------- equation

Now you can replace 6 for f to get the number of cars when the fee is $6

c = - 0.5 (6) + 25 = - 3 + 25 = 22 <---- this is the number of cars when fee is $6

Answers:

c = - 0.5 f + 25

number of cars = 22