Before Mount Everest was discovered, what was the highest mountain in the world?

A 3 digit number is such that it's unit digit is equal to the product of the other two digits which are prime. Also, the difference between it's reverse and itself is 396.

What is the sum of the three digits?

Give it food and it will live; give it water and it will die.

The doctor prescribed you to take one pill from the bottle every half an hour. The bottle is now left with only three pills.

How long do you think you have before you run out of pills?

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

What number comes next in the series?

5 15 5 18 5 24 14 20 _

Can you solve below mathematical equation?

2^1234 - 2^1233

A woman lives in a skyscraper thirty-six floors high and is served by several elevators which stop at each floor going up and down. Each morning she leaves her apartment and goes to one of the elevators. Whichever one she takes is three times more likely to be going up than down. Why?

There are 3 apples in the basket and you take away 2. How many apples do you have now?

A certain street contains 100 buildings. They are numbered from 1 to 100. How many 9's are used in these numbers?