Mental Exercise

1. Uncommon Spelling. Can you think of a common English word containing the letters "ie" which when the "ie" are reversed, results in another English word?

2. Unusual Sunrise. Once while I was travelling, I observed the sun rising in the west. How is this possible?

3. Hot Coffee. Suppose you are in the habit of pouring your coffee into a cup each morning and then drinking it a while later. You want to keep the coffee as hot as possible for when you start to drink it. You can put the cream in the coffee when you first pour it or a while later, just before you drink it. Which one will keep the coffee hottest for when you drink it?

4. Board Cut. Start with a wooden chessboard of 64 squares. Now try to separate it into 64 individual squares by cutting it with a saw. The task is to do this with as few cuts as possible. And yes, separate pieces may be stacked on top of one another as the board is separated into pieces.

5. Double Housing. A house is depicted by arranging eleven matchsticks to form the pattern shown below. How can just one match be moved so that it is changed into a depiction of two houses?

6. Which Switch. There are three light switches on a wall but just one of them controls an upstairs light bulb. The upstairs light is totally out of sight of the switches. In order to see the light you have to walk upstairs. Can you think of a way to guarantee that you will figure out which switch controls the light by making just one trip upstairs to check the light? Hint: light bulbs produce both heat and light.

7. Summer Soccer. There is a soccer league with ten teams. For the summer season, every team will play each of the other teams twice. How many total games will be played?

8. Number Guess. A number from one to ten is randomly chosen and two people try to guess the number. Whoever is closest wins. First one person makes a guess then the second person guesses a different number than the first person. Based on this, who has the advantage, the first guesser, the second guesser, or neither.

9. Magic Math. Choosing from among the digits 0 through 9, substitute a digit for each letter in the following calculation (same letter always becomes the same number):

10. Mystery object. Can you figure out what this is supposed to be? Lighter than what I am made of, More of me is hidden Than is seen.

Answer

1. Uncommon Spelling. The word is lie. Reverse the ie and you get lei.

2. Unusual Sunrise. I was travelling by plane. Just at sundown, the plane took off and as it rose, the sun appeared to move above the horizon.

3. Hot Coffee. The hotter coffee radiates heat faster and thus more heat. Therefore to keep the coffee the hottest, add the cream when you first pour the coffee rather than later.

4. Board Cut. If you always cut all the pieces in half, stacking all the pieces as you cut, it can be accomplished in six cuts.

5. Double Housing. The matchstick along the top is moved down to form another rooftop, making a second house:

6. Which Switch. Let's say the switches are labelled A, B, and C. Turn on switch A for one minute, then turn it off. Now, turn on switch B and go upstairs. If the light is on, then switch B is the one. If the light is off, feel the bulb, if it's warm, then it's controlled by switch A. If the bulb is cool, then switch C is the one.

7. Summer Soccer. The actual number of games is 90, not 180 as you might think.

8. Number Guess. The first person guesses either 5 or 6 to maximize the chances of winning. When the second guesser picks the one of these not chosen by the first guesser, neither person has an advantage.

9. Magic Math. 

10. Mystery Object. An iceberg