When the postman arrived at the Smith home to deliver mail through a slot in the front door, he was surprised to find the Smiths had acquired a vicious dog. The dog was fastened to a tree by a chain just long enough to reach the front door. The dog growled and bared its teeth.

How did the clever postman outwit the dog and reach the door safely?

You are standing in a pitch-dark room. A friend walks up and hands you a normal deck of 52 cards. He tells you that 13 of the 52 cards are face-up, the rest are face-down. These face-up cards are distributed randomly throughout the deck.

Your task is to split up the deck into two piles, using all the cards, such that each pile has the same number of face-up cards. The room is pitch-dark, so you can’t see the deck as you do this.

How can you accomplish this seemingly impossible task?

Susan and Lisa decided to play tennis against each other. They bet \$1 on each game they played. Susan won three bets and Lisa won \$5. How many games did they play?