Question

After the football game, the traffic out of the school parking lot is horrible! In fact, since the school is set off from town, the slow moving line of cars snakes back into town, bumper to bumper. The distance your car is from home is a linear function. When you have been crawling along for 10 minutes, you are 11 km from home, and when you have been driving for 15 minutes, you are 8 km from home. When (in minutes) will you reach home?

Answer 1

You went (11-8) km in 15 min
that is 3/15 = 1/5 km/min
you are 8 km from home
so
8 km = (1 km/5min) * x min
x = 5 * 8 = 40 min

Answer 2

The minutes are the x values and how far you traveled are the y values, so it is (10,11) and (15,8). Now you have to find the slope, which is -3/5. Plug all of the numbers into y=mx+b and you get 8=-3/5(15)+b. Once you solve that, b should equal 17. Now the equation is y=-3/5x+17. Plug zero into the y value and you should get 28.33 repeated for your answer. Round that to whatever place value your problem requires, mine was to the hundredth place so my answer was 28.33.

Answer = 28.33