What can you deduce from the following BrainBat?

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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?

Three doctors said that Bill was their brother. Bill says he has no brothers. How many brothers does Bill actually have?

What is the coolest letter in the alphabet?

Mr Black, Mr Gray, and Mr White are fighting in a truel. They each get a gun and take turns shooting at each other until only one person is left. Mr Black, who hits his shot 1/3 of the time, gets to shoot first. Mr Gray, who hits his shot 2/3 of the time, gets to shoot next, assuming he is still alive. Mr White, who hits his shot all the time, shoots next, assuming he is also alive. The cycle repeats. If you are Mr Black, where should you shoot first for the highest chance of survival?

I am a normal creature, but I have five hands. I can even have more but even then I will be considered normal.

Who am I?

A finger goes in me. You fiddle with me when you're bored. The best man always has me first. What am I?

Krish is 45 years old and his mother Crishtina is 73 years old.

Can you find out how many years ago, his mother was three times his age?

What does this simple rebus mean?

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