What is next number in the pattern below:

131 517 192 123 ?

Solve the mathematical equation in the picture below.

John was piloting a plane behind a car but was never able to overtake it. Why?

Before the start of the car race, John and Jacob have the same amount of fuel in their car. With this fuel, John can drive for 4 hours while Jacob can drive five hours.
After a time they realize that the amount of fuel left in John's car is 1/4th of the fuel in Jacob's.

For how long they are racing?

I am a white box having no key or lid.
Yet there is a golden treasure inside it.

What Am I?

How many squares, of any size, can you find on this chessboard which do not contain a Rook?

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?

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

I know a 5-digit number having a property that With a 1 after it, it is three times as large as it would be with a one before it.

Guess the number?

A man is found hanging dead from the ceiling of a room. The room’s dimensions are 15 x 15 x 15. The man is only 6ft tall and the rope was only 2ft long. There are no windows and only one door to the room. The door is bolted shut from the inside, and a puddle of water is under the man. How did he kill himself?