[bd2312]

I don't get my homework. "Driving from Chicago to Detroit one day, Ricardo covered the 250 miles in five hours. Because of heavy traffic, the 250 mile return took six hours and fifteen minutes. Calculate average speed for the trip to Detroit,the trip from Detroit, and the round trip." It says that there are multiples answers to this and I have to explain why the terminology average speed is a bit misleading. Can someone please explain to me. I know that I have to use the formula distance divide by time equal speed but I don't know how to use that.

[ebaines]

I'll walk you through a different example, and you can use that technique to do your homework.

Suppose you travel 100 miles in 2 hours. Your average speed during the trip is found by dividing the distance by time, as you know:

Average speed = distance/time = 100 miles/2 hours = 50 Miles per hour.

If you continue on a second segment of 100 miles and that segment takes 4 hours, your average speed for that 2nd segment is 100 miles/4 hours = 25 miles per hour.

To find the average speed for both segments divide the total distance traveled by the total time taken:

Average speed for both segments = (100 miles + 100 miles)/(2 hours + 4 hours) = 200 miles/6 hours = 33.3 miles per hour.

As for the term "average speed" being misleading; there are a couple of things. First, when Ricardo gets to Detroit what does he do? Does he turn right around and drive back, or does he hang out a while? Should the time he spends in Detroit before heading back be counted in the total elapsed time? Also - when he gets back to Chicago he's right back where he started from, so you could argue that the total distance traveled from beginning to end is 0 miles - after spending 11 hours driving he got no further than someone standing still.

[joypulv]

If I go 50 miles in 1 hour, that's 50 miles an hour, right? (Average)
250 miles in 5 hours, what do you think is the average speed? Like you said, distance divided by time.
For the division of the return, just use 6.25 as your divisor.
For the whole trip, add all the miles and divide by all the time.
So you have 3 answers, no more, no less.

I see nothing 'misleading' about average.
Average means just what it says, despite stop signs and steep turns that you slow down on; you go faster other times. Average is the total of something divided by some unit, like time.