Good Riddles

Question: someone came into my shop and stole 100 dollars from the register without my knowledge. the person came back 5 minutes later with the same 100 dollars and bought 70 dollars in items and i gave him back 30 dollars change. How much did i lose?

Question: I move faster in certain solids, but slower in certain gases. I am typically broken by objects with large masses. I can be used as for pleasure, practice, and even an alarm. If used excessively, I can cause harm. What am I?

Question: A mirror for the famous, but informative to all.
I'll show you the world, but it may be a bit small.

What I am?

Question: Alone I am 24th, with a friend I am 20. Another friend and I am unclean.What am I?

Question: A man is doing some work on his home and goes to a hardware store. He goes up to the clerk and tells him what he wants. The clerk tells him that each one is $1. He tells the clerk he would like 5000 and he is charged only $4.

What did he buy?