When the cost of a car wash was $8, there were 90 customers. When the cost was reduced to $4, there were 170 customers. Assume the relationship is linear.

Question

anonymous · Answer

@iGreen

igreen · Answer

What's the question? It just says to assume the relationship is linear..

igreen · Answer

You have two points on a graph. (8, 90) and (4, 170).

anonymous · Answer

A line models the relationship between the cost, x, and the number of customers, y. What is the slope of the line?

anonymous · Answer

^^^ the Question

igreen · Answer

You have to find the slope between (8, 90) and (4, 170).

To do that you have to use the slope formula, $m = \dfrac{y_2-y_1}{x_2-x_1}$.

In this case:

$y_2 = 170$
$y_1 = 90$

$x_2 = 4$
$x_1 = 8$

Plug them in:

$m = \dfrac{170-90}{4-8}$

Subtract:

$m = \dfrac{80}{-4}$

$m = -20$

So the slope is -20.