What is next number in the pattern below:

131 517 192 123 ?

I am white when I am dirty, and black when I am clean. What am I?

The Puzzle: A girl, a boy, and a dog start walking down a road.

They start at the same time, from the same point, in the same direction.

The boy walks at 5 km/h, the girl at 6 km/h.

The dog runs from boy to girl and back again with a constant speed of 10 km/h. The dog does not slow down on the turn.
How far does the dog travel in 1 hour?

Find The Next Number in the series:

12 13 15 17 111 113 117 119 123 ?

What can you catch but never throw?

What is the centre of gravity?

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

Can you find the company name in the pictogram below?

I have feet, but no legs. Which animal Am I?

Can it be possible to build a house that has all its four walls facing towards the South?