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

What has lots of eyes, but can’t see?

John is looking at Jenifer, but Jenifer is looking at Jacob. John is married, but Jacob is not.

Is a married person looking at an unmarried person ?

A man has a barrel filled with oil that weighs 100 pounds, and then he puts something into it. Now the barrel weighs less than 100 pounds. What did he put in the barrel?

How can you make number one disappear by adding something to it?

There is one thing that goes round the house and also inside the house but never even share a brief touch. What is it?

Can you arrange four 9's and use at most 2 math symbols, to make the total 100?

Three fair coins are tossed in the air and they land with heads up. Can you calculate the chances that when they are tossed again, two coins will again land with heads up?

What is the difference between a jeweller and a jailer?

Can you count the number of triangles in the given figure?