What four weights can be used to balance from 1 to 30 pounds?

What month of the year has 28 days?

A large water tank has two inlet pipes (a large one and a small one) and one outlet pipe. It takes 3 hours to fill the tank with the large inlet pipe. On the other hand, it takes 6 hours to fill the tank with the small inlet pipe. The outlet pipe allows the full tank to be emptied in 9 hours.

What fraction of the tank (initially empty) will be filled in 0.64 hours if all three pipes are in operation? Give your answer to two decimal places (e.g., 0.25, 0.5, or 0.75).

In the given figure, you can see that four match sticks are used to form a square. Can you form five squares by using six matches?

Two guards were on duty outside a barracks. One faced up the road to watch for anyone approaching from the North. The other looked down the road to see if anyone approached from the South. Suddenly one of them said to the other, "Why are you smiling?"

How did he know his companion was smiling?

I can write cow in 13 letters.

Can You?

Can you think of a smallest +ve number such that if we shuffle the digits of the number, the new number becomes double the original number?

What brings you down but never up?

Can you tell a 3D object that has just two surfaces?

Can you find out which number multiplied by itself will give the output as 12345678987654321?