How can one talk without saying a single word?

A tree doubled in height each year until it reached its maximum height over the course of ten years. How many years did it take for the tree to reach half its maximum height?

How could a baby fall out of a twenty-story building onto the ground and live?

Find the mistake in the below maths equations

A = 2
A(A-1) = 2(A-1)
A2-A = 2A-2
A2-2A = A-2
A(A-2) = A-2
A = 1

There are two candles. Both will only burn exactly for an hour. How will you use these two candles to measure forty-five minutes?

Can you divide the below-given shape into four equal and identical pieces?

A man dies of old age on his 25 birthday. How is this possible?

Three people enter a room and have a green or blue hat placed on their heads. They cannot see their own hat but can see the other hats.
The colour of each hat is purely random. They could all be green, blue, or any combination of green and blue.
They need to guess their own hat colour by writing it on a piece of paper, or they can write 'pass'.
They cannot communicate with each other in any way once the game starts. But they can have a strategy meeting before the game.
If at least one of them guesses correctly they win $10,000 each, but if anyone guesses incorrectly they all get nothing.
What is the best strategy?

What is the word or phrase?

No matter how little or how much you use me, you change me every month. What am I?