glassynails wrote:guitareleven wrote:glassynails wrote:... If I have to drive 100 miles in 1 hour and the first 1/2 hour I end up only going 20 miles I must've "averaged" 20mph. So in order to get to my 100 mile mark in 1/2 hour remaining I have to drive 160 mph. .

If you travel 20 miles in half an hour, your average speed is 40 miles an hour, not 20. But according to what you said, you only maintained that average for

half an hour, which is why your distance traveled at that point is only 20 miles, and not 40. So, you are right about the rest of it; having traveled 20 of your intended 100 miles leaves you 80 to go; to accomplish that in half an hour, you would then, as you say, have to average 160 miles an hour for the rest of the trip.

I meant I averaged 20 mph in the half hour.

But you didn't. You averaged 40 mph. Had you maintained that average of 40 mph for an hour, as in"miles per

hour" then you would have gone 40 miles. But , you maintained that average of 40 mph for only half an hour. Therefore, the distance you traveled, in that half hour of averaging 40 miles an hour, was half of 40, which, as you stated, was 20 miles. If you like, instead of stating it in terms of "mph", which is "miles per hour", then you can state it it in "mp½h", which is "miles per

half hour". This is a non-standard measurement, but is just as accurate, and

then, if that's what you want, you get to speak of your average as having been 20. You just have to clarify the departure from standard if what you also want is to be understood.