Calculators can be used for fun as well as for doing math calculations.
While calculators are a useful tool for doing complicated sums and calculations, they can also be used to play funny tricks on your friends. These tricks are all simple and easy to perform but can have astounding results. They will leave your friends scratching their heads trying to work out how you did it.
Predicting Numbers
This trick will give your friends the impression that you are either a magician or a clairvoyant, when in fact the answer was predictable all along. Give your friend a calculator and ask him to enter a three-digit number where the digits are in descending order, for example 532, without telling you what the number is. Then ask him to reverse the order of the digits and subtract the new number from the original. For this example, your friend would subtract 235 from 532, leaving him with 297. Then ask your friend to add this number to its reverse. Before he tells you what the final number is, tell him that you predict the number to 1,089. With this type of sum the answer is always 1,089, but your friend will think you are psychic.
Guess the Secret Number
Ask a friend to choose a whole number between 1 and 20 and hide it from you. Then give him a calculator and ask him to multiply this number by three, then add the original number and subtract five. Then ask him to multiply this number by three again, before multiplying it by three for a third time. Ask him to add the secret number again and then subtract the number of their favorite month, before multiplying the number by three, three more times. Ask him to add the secret number again and then subtract his favorite day of the month. When your friend shows you the final total on the calculator display, if it is negative his original number was one; if it is only three digits long his number was two. For other numbers, ignore the final three digits, add two and this will be his secret number.
The Inventor and the Emperor
There is a legendary story about the inventor of chess receiving a reward from the emperor of India. The emperor is shocked when the inventor merely asks for a grain of rice to be placed on the first square of the chessboard, two on the second square, four on the third square and so on, doubling the number of rice grains on each square. You can trick your friends with this principle. Give them several bags of rice and ask them to fill the chessboard in this way; like the emperor they will probably find it very easy until they realize that they are running out of rice. Then you may step in and use your calculator to show your friends how much rice would be required to fill the chessboard. Start with 1 and use the calculator to repeatedly multiply that number by 2. The emperor from the story discovered that it would be more rice than the whole of India would be able to produce in many centuries.
Calculator Words
Making words on a calculator is a fun way to amuse your friends. On traditional "seven-segment" calculators, certain numbers look like letters when turned upside down. This allows you to make words from certain longer numbers. For example, 07734 makes the word "hello" when turned upside down, while the 37818 makes the word "Bible." See how many words you and your friends can come up with.
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