A new Engineering building containing 100 offices had just been completed. John was hired to paint the numbers 1 to 100 on the doors. How many times will John have to paint the number nine (9)?

The person who makes it has no need for it; the person who buys it has no use for it. The person who uses it can neither see nor feel it. What is it?

Until it is measured, not known. Yet how you miss it when it has gone. What is it?

I had an infinite supply of water and 5 litres and 3 litres jars.

How would you measure exactly 4 litres in the least number of steps?

A doctor and a boy were fishing. The boy was the doctor’s son, but the doctor was not the boy’s father. Who was the doctor?

What number comes next in the series?

5 15 5 18 5 24 14 20 _

What jumps when it walks and sits when it stands?

I am weightless, but you can see me. Put me in a bucket, and I'll make it lighter. What am I?

Nine marbles are arranged in the image below. Can you slide two marbles to form a square?

People put me on the table and cut me but do not eat me. What am I?