Distance Rate Difference

Question

You are taking a road trip and drive 500 miles in 8 hours the first day. On the second day, you drive

300 miles in 6 hours. What is the difference in speed between the two days of travel?

500 300

— - _____

8 6

62.5− 50 = 12.5

There is a difference of 12.5 mph between the two days.

I don't understand how the answer was computed.

Answer 1

Well, 300 divided by 6 is 50. That should be pretty clear since 6 times 50 is 300.

500 divided by 8 is the same as 250/4 which is the same as 125/2. If you aren't allowed to use a calculator and you have forgotten how to do long division, you can rewrite this as (120+4+1)/2 = 120/2 + 4/2 + 1/2 = 60 + 2 + 0.5 = 62.5.

Finally, 62.5 - 50 = (50 + 10 + 2.5) - 50 = 12.5.