If it took eight men ten hours to build a wall, how long would it take four men to build it?

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

What has one letter and starts with an E?

Can you make a six-letter word using the letters N, A and B ?

I have a five and a three-gallon jar. Assuming there is an infinite supply of water, how can I measure one-gallon water?

Take away the whole and some still remain. What is it?

A donkey is behind another donkey
I'm behind that second donkey
But there is a whole nation behind me

It is a murder you can describe in a word.

One absent-minded ancient philosopher forgot to wind up his only clock in the house. He had no radio, TV, telephone, internet, or any other means for telling time. So he travelled on foot to his friend's place a few miles down the straight desert road. He stayed at his friend's house for the night and when he came back home, he knew how to set his clock. How did he know?

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

I have two sand hourglasses:
1. A 7 minute one and
2. An 11-minute one.

Using just these 2 sand hourglasses, how can I measure time as 15 minutes?