Which number should replace the question mark?

I am a white box having no key or lid.
Yet there is a golden treasure inside it.

What Am I?

What number should come in place of the question mark below?

Can you find a five letter word that is left with only two letters if one is removed?

Solve the following series:
AZ, GT, MN, __, YB

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

Paul's height is six feet, he's an assistant at a butcher's shop and wears size 9 shoes. What does he weigh?

A game is being played where eight players can last for thirty-five minutes. Six substitutes alternate with each player in this game. Thus, all players are on the pitch for the same amount of time including the substitutes.

For how long is each player on the pitch?

What is more useful when it is broken?

Double it and multiply it by 4. Then divide it by 8 and you’ll have it once more. What number is it?