Riddle #3612

Question: If I am buying 9 for $1, 18 for $2, 125 for $3, and 1222 for $4, then what am I buying?

Question: 8,549,176,320 What makes this number unique?

Question: Hard, Harder, and Hardest are brothers. By age from youngest to oldest, it goes Hard, Harder, Hardest. Hard is half the age of Hardest who is 20 which means hard is 10. Harder has a two-year difference between the number of years older he is than Hard and the number of years younger he is than Hardest. Harder is closer to the age of Hard than Hardest. How old is Harder?

Question: When is 99 more than 100?

Question: What are the next two letters in the following series and why? WATNTLITFS__

Question: You have a glass of water that looks about half full. How can you tell, only using the glass of water itself, if the glass is half full or not?

The glass is a right cylinder.