1. Please turn off your computers… …we will play a little game first 

2. The Row Boat Puzzle

3. The Row Boat Puzzle A man rows a boat in a river
The man must row from point A to point B
The water in the river steams in the direction from A to B, with constant speed
The man rows the boat with constant speed

4. The Row Boat Puzzle A B
Due to the stream, it takes less time to row from A to B, than from B to A
It takes 6 minutes to row from A to B
It takes 12 minutes to row from B to A
QUESTION: How long will it take to row from A to B, if there was no stream…?

5. The Row Boat Puzzle Hint #1 Call the speed of the rower R
Call the speed of the stream S
Total speed from A to B: R+S
Total speed from B to A: R-S
Total speed without stream: R

6. The Row Boat Puzzle Hint #2 Distance = Speed x Time
The distance A to B is called L, then:
L = (R + S) x 6 minutes
L = (R – S) x 12 minutes
Find S expressed by R

7. The Row Boat Puzzle Hint #3 S = 1/3 R, so by inserting this:
L = 4/3 R x 6 minutes
L = 2/3 R x 12 minutes
We must then solve L = R x ? minutes