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

1. Pleaseturnoffyour computers……wewillplay 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 A B

4. The Row Boat Puzzle • 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…? A B

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