If you had a pizza with crust thickness 'a' and radius 'z', what's the volume of the pizza?

How many pluses should we put between the digits of 987654321 to get a total of 99, and where?

Can you find out the smallest number that can be conveyed as the sum of three squares in three unique ways?

What is 3/7 chicken, 2/3 cat and 2/4 goat?

A girl rode into a tourist spot out of the city on Thursday. She loved the place and decided to stay for a few days. She stayed for four days and then she left for back home on Thursday.

How can this be possible?

How many cubic feet of dirt are in a hole of one foot deep, three feet long, and two feet wide?

I cry without having a voice.
I fly without having wings.
I bite without having teeth.
I whisper without a mouth.

Who am I?

Take 9 from 6, 10 from 9, 50 from 40, and leave 6.

How Come ??

A man started to town with a fox, a goose, and a sack of corn. He came to a stream which he had to cross in a tiny boat. He could only take one across at a time. He could not leave the fox alone with the goose or the goose alone with the corn. How did he get them all safely over the stream?

Assume there are approximately 5,000,000,000 (5 billion) people on Earth. What would you estimate to be the result, if you multiply together the number of fingers on every person's left hand? (For the purposes of this exercise, thumbs count as fingers, for five fingers per hand.) If you cannot estimate the number then try to guess how long the number would be.