How many words can a pen with half refill write?

Look at this sequence from top to bottom. What is the next number in the sequence?
1
11
21
1211
111221
312211

Find the missing number in the sequence below:

A man and a dog were going down the street. The man rode, yet walked. What was the dog’s name?

I am taken from a mine and shut up in a wooden case, from which I am never released, and yet I am used by almost every person. What am I?

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

Can you solve the maths in the below-given picture equation?

A bag contains 64 balls of eight different colours. There are eight of each colour (including red). What is the least number you would have to pick, without looking, to be sure of selecting 3 red balls?

You are confined in a room and given two metal rods. Out of these two rods, one is magnet and the other is the iron rod. They look starkly similar. You don't have any other metal object in the room.

How will you decide which one of those is magnet?

Can you find the key in the picture below?