I have eight fingers and two thumbs but I do not live. What Am I?

When Jack was six years old he hammered a nail into his favourite tree to mark his height. Ten years later at age sixteen, Jack returned to see how much higher the nail was. If the tree grew by five centimetres each year, how much higher would the nail be?

When I go in I might cause pain. I cause you to spit and ask you not to swallow. I can fill your hole. What am I?

Once upon a time, there was a castle on a square island. The entire island was surrounded by a 14m wide trench. The Romans had wanted to invade the castle and had brought a few wooden planks along with them to facilitate themselves in crossing the moat. The planks were however found to be only 13m long.

The Romans still managed to cross the trench. How did they do it?

I speak without a mouth, and hear without ears. I have no-body, but I come alive with the wind. What am I?

During which month do people sleep the least?

Can you find out which triangle will have a bigger area among the following?
1. A triangle with sides 300, 400 and 500
2. A triangle with sides 300, 400 and 700

What number comes next in this sequence:
7 8 5 5 3 4 4 _

I know there are two methods by using three time the same number with a plus(+) operator , you can make sum as 60.

One of them is 20+20+20.

whats the other way ?

I know a country, If you remove the last alphabet of its name, it will become a part of your body. Do you name it?