During which month do people sleep the least?

What has a ring but no finger?

If,
29 - 1 = 30
9 - 1 = 10
14 - 1 = 15

Based on similar logic, Can you prove that the below algebraic equation is true?
11 - 1 = 10 ?

A game is being played where eight players can last for thirty-five minutes. Six substitutes alternate with each player in this game. Thus, all players are on the pitch for the same amount of time including the substitutes.

For how long is each player on the pitch?

In two decks of cards, what is the least amount of cards you must take to be *guaranteed* at least one four-of-a-kind?

The person who makes it has no need for it. He who purchases it does not use it. The person who does use it does not know they are. What is it?

What number does the below three word/phrase identify and why?
1. Deck
2. Year
3. Singing in the Rain

Many have heard it, but nobody has ever seen it, and it will not speak back until spoken to. What is it?

Buy me, smell me or deliver me, I do not change.

Who am I?

There was once a college that offered a class on probability applied to the real world. The class was relatively easy, but there was a catch. There were no homework assignments or tests, but there was a final exam that would have only one question on it. When everyone received the test paper it was a blank sheet of paper with a solitary question on it: 'What is the risk?'.Most students were able to pass, but only one student received 100% for the class! Even stranger was that he only wrote down one word!
What did he write?