Jim paddels from one shore of a lake three miles wide at 4 mph, and john paddels from the opposite shore at 5.

Question

How long will they travel before they meet?

I would like to know how to do it though, everything I've tryed dosnt work out right!

Answer 1

3miles across they will be meeting when their combined distance travelled is 3 miles. The time (t) must be the same for both of them and is the common factor.

Therefore:

3 = t*4mph+t*5mph   OR

3= t* (4mph+5mph)

3= t*9

1/3 = t

1/3 of one hour = EXACTLY 20 minutes

(fractions occur when using a calculator)

HTH

Answer 2

4mph=351999 feet/ min 5mph=440 feet/min. Their combined speed is 791.999 feet per minute.   3 miles is 15840 feet  So divide 15840 by 791.999 and you get 20minutes and less than a 100th of a second.

Answer 3

disclaimer:  Logician not a mathematician

5 mph + 4 mph = 9mph approach speed. If they travel a total of 3 miles they will meet in 3/9 or 1/3 hours or 20 minutes.

1/3 hour  X 4 miles per hour = 4/3 miles or 1 1/3 miles for Jim

1/3 hour X 5 miles per hour = 5/3 miles or 1 2/3 miles for John

Check: 4/3 Miles + 5/3 miles = 9/3 miles = 3 miles = the distance across the lake.