Solve below rebus puzzle?

I am the one who remains awake when you sleep. But I need to rest when you awake. Who Am I?

John drives to his office at 20km/hr. After reaching the office, he realizes that today is a holiday. He went back at an average speed of 30km/hr. Discounting the time spent in the stoppage what was the average speed of his journey?

If 5 cats catch 5 mice in 5 minutes, how long will it take one cat to catch a mouse?

You knock a Table over in the library, and suddenly 20 eyes are looking at you.

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?

In a jungle where there are no street lights or any other artificial source of lights, I notice a black snake crossing the road.
How did I get sight of the snake?

Solve the below puzzle by replacing the question mark with the correct number.

3 6 12

4 8 16

5 10 ?

What word begins and ends with an E, but has only one letter?

John left on a horse on Thursday , was gone for two days, and came back on Thursday after completing his work. How did that happen?