Question

The stopping distance on wet pavement at 20mph is about 60feet. The stopping distance at 30mph is 120feet. What would you estimate the stopping distance is at 40mph? Construct a formula

Answer 1

`y = 6x - 60` --- formula

The stopping distance at 40mph is 180ft

Explanation:

Given

`(x,y) = (20,60)`

`(x,y) = (30,120)`

Solving (a): Construct a formula

Calculate the slope (m)

`m = (y_2 - y_1)/(x_2 - x_1)`

`m = (120 - 60)/(30-20)`

`m = (60)/(10)`

`m=6`

So, the equation is:

`y = m(x - x_1) + y_1`

`y = 6(x - 20) + 60`

Open bracket

`y = 6x - 120 + 60`

`y = 6x - 60`

Hence, the formula to use is:
`y = 6x - 60`

Solving (b): y, when x = 40

`y = 6x - 60`

`y = 6 * 40 - 60`

`y = 180`