Jim paddle from one shore of a lake three miles wide at 4 mph, and john paddles from the opposite shore at 5 mph. how long will they travel before they meet?

Let us assume that the distance travelled by Jim to meet John = X miles

Then the distance travelled by John to meet Jim = (3 - X) miles

We already know the equation

Time = Distance travelled / Speed

Then for Jim,

Time = X/4

For John

Time = (3 - X) / 5

As they meet, so they must have travelled the same amount of time.

Then

X/4 = (3 - X) / 5

X = (12-4X) / 5

5X = 12 - 4X

9X = 12

X = 12/9

= 4/3

= 1.33 miles

Now our target is to find the amount of time after which Jim and John meet.

Then

Time = X/4

= 1.33/4

= 0.33325 hours

= (0.33325 * 60) minutes

= 19.995 minutes.

So it can be safely assumed that Jim and John will meet after a period of 20 minutes.