Easy Riddles and Answers

Question: You wait for it. It cracks, stays for a moment, and then vanishes before your eyes. What is it?

Question: If 1/2 of 5 is 3, then what is 1/3 of 10?

Question: John has been hired to paint the numbers 1 through 100 on 100 apartments.

How many times with he have to paint 8?

Question: I am a big threat to humanity,
but you wouldn't get rid of me even if you could.

What am I?

Question: Using 3 periods (.) and 1 question mark (?) make this a logical and grammatically correct sentence:

"That that is is that that is not is not is that it it is"