How do you go from 98 to 720 using just one letter?

I am weightless, but you can see me. Put me in a bucket, and I'll make it lighter. What am I?

John enters a small room. The Door Closes.
When the door opens, John is in a larger room.

Explain?

It is a six-letter word.
The first four letters are me.
The second and last letters are the same.
The fourth second and last letter is payment.

Who is it?

What is more useful when it is broken?

There’s a girl who has a large family. She has an equal amount of brothers and sisters, but each brother only has half as many brothers and sisters. What’s the correct amount of brothers and sisters?

What building has the most stories?

In particular commonwealth games, a female participant won silver and gold medals for a single event.

How can this be possible?

The first two letters signify a male, the first three letters signify a female, the first four letters signify a great, while the entire world signifies a great woman. What is the word?

What is black when you buy it, red when you use it, and gray when you throw it away?