Question

If Rick buys 50 tennis balls, he pays $30. If he buys only 40 tennis balls from the same store, he pays $20. Assuming that the pricing follows a linear model, what is the model?

Answer 1

y = 100x - 10

Explanation:

Let 'x' be the number of tennis balls, therefore:

50x = $30 -> x = $0.6

40x = $20 -> x = $0.5

Therefore, we have the following two points:

(0.6, 50) and (0.5, 40)

The slope is:

m = (y2 - y1)/(x2-x1) = 10/0.1 = 100

The equation of the line is:

y - y0 = m(x-x0)

y = 100(x-0.5) + 40

y = 100x - 10