You have a five cup mug, a three cup mug, a water supply, a sink with a drain, and a packet of instant coffee which when dissolved in one cup of water produces coffee of strength 100%.

The packet may be used at any time, but the entire contents of the packet must be dissolved into a single mug when it is used.

Your task is to fix 4 cups of coffee at exactly 16% strength.

(In reply to re: i think i got one by ThoughtProvoker)

good point. so the complete steps are:

1. fill 5 cup mug
2. pour 3 cups from 5 cup mug to 3 cup mug
3. empty 3 cup mug
4. pour 2 cups from 5 cup mug to 3 cup mug
5. fill 5 cup mug
6. pour coffee packet into 5 cup mug
   ( 1 packet into 5 cup mug = 5 cups of 20% strength )
7. since there is already 2 cups in the 3 cup mug, we can pour just 1 cup from 5 cup mug into 3 cup mug
   4 cups of 20%
8. empty 3 cup mug
9. pour 1 cup from 3 cup mug to 5 cup mug
10. empty 3 cup mug
11. fill 3 cup mug with water
12. pour 1 cup from 3 cup mug to 5 cup mug.
13. pour 1 cup from 5 cup mug to 3 cup mug.

Posted by bin zhu on 2004-06-28 13:24:34