Speed/Distance Riddle

If you mean:
If Jim drives from Point A to Point B at 40 miles an hour in 10 minutes, how fast does he have to drive the return trip from Point B to Point A for the average speed of the total time he spent driving was 30 miles an hour?

then:
2/30 = 1/40 + 1/S
S = 24 mph

Re: Speed/Distance Riddle



Francisco, are you related to Frankie A? You should post in the Humour forum. Wicked.

Thanks for the edit, markr, I forgot to include the bit about the return trip.
That answer, however, is incorrect! I'll give you the right answer soon.

And, Tryagain, no relation to the venerable Mr. Apisa - but I'll take it as a compliment!

I'm curious to see the trick I missed.

distance = 40/6 = 6 2/3 miles

total distace both ways = 2 * 6 2/3 = 13 1/3 miles

he's driving this at 30 mph, so his total time is 13 1/3 / 30 = 4/9 of an hour = 26 2/3 minutes

he did the first part in 10 minutes, so the way back is going to be in 16 2/3 minutes, or 5/18 of an hour

6 2/3 miles divided by 5/18 of an hour is 24.

Where's the mistake?

huh - I think I gave the riddle wrong. I'm batting zero. That does work out.