Can you arrange four 9's and use at most 2 math symbols, to make the total 100?

Can you name an animal whose killing cannot be performed without spilling your own blood?

10+10 and 11+11 can give you the same answer.

Explain how?

You stand in front of two doors. A guard stands next to each door. You know the following things: one path leads to paradise, the other leads to death. You cannot distinguish between the two doors. You also know that one of the two guards always tells the truth and the other always lies. You have permission to ask one guard one question to discover which door leads to paradise. What one question would you ask to guarantee you enter the door to paradise?

I am a type of vehicle that has two wheels and is powered by humans. What am I?
Hint 1: You can ride me for exercise.
Hint 2: I am environment-friendly.

A Man gave one of his sons 10 cents and another son was given 15 cents. What time is it?
Hint: Figure out the relation between time and number, is not so easy..:)

I’m light as a feather, yet the strongest person can’t hold me for five minutes. What am I?

Can you decipher the two rows to find the hidden word?

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

If I put in one canary per cage, I have one bird too many. If I put in two canaries per cage, I have one cage too many. How many cages and canaries do I have?