What always comes into a house through the keyhole?

You have a three-gallon and a five-gallon measuring device. You wish to measure out four gallons.

A man dies of old age on his 25 birthday. How is this possible?

Find out a multi-digit number that if multiplied by the number 9 or any of its multiplications products (i.e. 18, 27, 36, 45,..) will result in the multiplication factor repeated (n) number of times.

Which letter of the alphabet has the most water?

You see a boat filled with people, yet there isn’t a single person on board. How is that possible?

A wealthy man lives alone in a small cottage. Being partially handicapped he had everything delivered to his cottage. The mailman was delivering a letter one Thursday when he noticed that the front door was ajar. Through the opening he could see the man's body lying in a pool of dried blood. When a police officer arrived he surveyed the scene. On the porch were two bottles of warm milk, Monday's newspaper, a catalog, flyers, and unopened mail. The police officer suspects it was foul play. Who does he suspect and why?

John is the son of Jacob.
So,
Jacob is the_____of John's father?

There are 2 people near the river and both of them want to get on the other side. The boat can only take one of them. But they got across.
How?

What does a man do only once in his lifetime, but women do once a year after they are 29?