A merchant has 21 sacks of grain: 7 full, 7 half-full and 7 empty. He wants to divide them equally among his three sons. How can he do this, without transferring any grain between sacks, so each son has the same quantity of grain and number of sacks?
There is an abandoned aquarium in an empty house. The aquarium has three large fish and three small fish. But after a week, one large fish and two small fish die.
A black dog is sleeping in the middle of a black road that has no streetlights and there is no moon. A car coming down the road with its lights off steers around the dog. How did the driver know the dog was there?
Supposedly this is given as a test in Japan. I have no idea if that’s accurate.
There are 8 people who have to cross the river on a raft.
1. Policeman 2. Thief 3. Father 4. Boy 1 5. Boy 2 6. Mother 7. Girl 1 8. Girl 2
The rules are:
Only two people can cross at a time. Only the adults can operate the raft. The father can’t be with the girls unless the mother is there. The mother can’t be with the boys unless the father is there. The thief can’t remain with anyone unless the policeman is present.