A 400 yard long train, travelling at 30 mph, enters a 4.5 mile long tunnel.
How long will elapse between the moment the front of the train enters the tunnel and the moment the end of the train clears the tunnel?
Two men ride their horses to the town blacksmith to ask for his daughter's hand in marriage. To help decide who will get to marry her, the blacksmith proposes a very strange race:
"You will race your horses down the mile-long road from here to the center of town, and the man whose horse passes through city hall's gates LAST will get to marry my daughter."
The men have no idea how to proceed, but after a few minutes of thinking, they come up with a great idea to abide by the blacksmith's rules. 30 minutes later, one of the men is gloating, having won the daughter's hand in marriage.
What was the idea the men had?
Each man rides the other man's horse. They race as they normally would. The blacksmith said the man whose horse crosses last would win, so the man who wins the race would have his horse finish last.
You have two jugs, one that holds exactly 3 gallons, and one that holds exactly 5 gallons. Using just these two jugs and a fire hose, how can you measure out exactly 4 gallons of water?
Fill the 5-gallon jug to the top, and then pour it into the 3-gallon jug until the 3-gallon jug is full. You now have 2 gallons remaining in the 5-gallon jug. Pour out the 3-gallon jug, and then pour the 2 gallons from the 5-gallon jug into the 3-gallon jug. Finally, fill the 5-gallon jug to the top and pour it into the 3-gallon jug until it's full. Since there was only space left for 1 more gallon in the 3-gallon jug, you now have exactly 4 gallons in the 5-gallon jug.