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

In a boat, the father of a sailor's son is sitting with the son of the sailor. However, the sailor is not present on the boat.

Can this even be possible?

How many triangles can you find in this given picture?

If you're 8 feet away from a door and with each move you advance half the distance to the door. How many moves will it take to reach the door?

I have no doors but I have keys, I have no rooms but I have space, you can enter but you can’t leave! What am I?

I have lakes with no water, mountains with no stone and cities with no buildings. What am I?

A brand new Mobile Phone was on sale at 20% as a promotional offer. By what per cent must the Mobile price be increased to sell it at the original price again?

Spot 5 differences in two Christmas tree below:

There are forty elephants and they have forty-fore heads. How can this be possible?

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