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

If you’ve got me, you want to share me; if you share me, you haven’t kept me. What am I?

Which wheel of car does not rotate when you turn your car right?

You have two rectangular wires.

Both of them have property that when you light the fire from one end , it will take 60 minutes to get completely burn.

However, they do not burn at consistent speed (i.e it might be possible 1st 20% burn in 50 minutes and 80% can burn in 10 minutes).

So how could you measure 45 minutes ?

Solve the mathematical equation in the picture below.

The square root of number 121 is "11". What is the square root of the number "12345678987654321."?

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

By what process could you make a 'Tea-Table' into food?

They came out at night, without being called.
They lost at day, without being stolen.
Who are they?

The chance of Mr John winning the lottery is 10%. All participants lined up and Mr John is 4th in the row. The first three participants lose the lottery.

What is the chance of Mr John now?