Good Riddles

Question:

Take me for a spin and I'll make you cool,
but use me when it's cool and you're a fool.

What am I?

Question:

What is the most common use of cowhides?

Question:

The dirtier I am, the whiter I get,
Leave a mark on me when you stand, I'll leave a mark on you when you sit.

What am I?

Question:

Sad, sick, or sloppy I'll help you out,
Use me right and I'll cover your snout.

What am I?

Question:

John has some chickens that have been laying him plenty of eggs. He wants to give away his eggs to several of his friends, but he wants to give them all the same number of eggs. He figures out that he needs to give 7 of his friends eggs for them to get the same amount, otherwise there is 1 extra egg left.

What is the least number of eggs he needs for this to be true?