Name a key which is hardest to turn.

Can you solve this amazing hard number series problem?
7, 8, 10, 12, 16, 18 ?

How many bananas can you eat if your stomach is empty?

My thunder comes before the lightning; my lightning comes before clouds; my rain dries all the land it touches. What am I?

What is next number in the pattern below:

131 517 192 123 ?

You have two buckets of 11 liters and 6 litres.
How can you measure exactly 8 litres?

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?

Three brothers Jacob, John, and James live in Mexico City. The product of the ages of these brothers is 175. Jacob and John are twins. How old is James?

John enters a small room. The Door Closes.
When the door opens, John is in a larger room.

Explain?

A four-digit number (not beginning with 0) can be represented by ABCD. There is one number such that ABCD=A^B*C^D, where A^B means A raised to the B power. Can you find it?