Our old women **calculators** from school, institute or university still have a lot to say in our daily lives; and thanks to them we can surprise our friends and family with all kinds of games with the calculator, each one more ingenious. Now we want to offer you **the definitive mathematical and calculation tricks**, 8 ways to leave locals and strangers speechless with **clever number puzzles** to which we can resort to make the encounters with our loved ones more enjoyable. In addition, we offer you a small **extra trick on the calculator iPhone**, something that you probably don't know despite being a user **iOS**. Next, **the best math tricks with a calculator**.

## The best math tricks with a calculator

## The mystery of the number 73

- Write the number 73 on a piece of paper; without showing it to anyone, fold it and give it to someone.
- Ask the person to think of a four-digit number and enter it twice in a row into the calculator (for example, 12341234).
- Tell him to divide the number by 137.
- Now tell him he can divide the result by its original four-digit number; ask him to check the folded paper (73).
- The number 73 will appear on both the calculator and the paper.

## Cycle 421

- Choose a number and enter it into the calculator.
- If it is even, divide it by 2, if it is odd, multiply it by 3 and add 1.
- Repeat the process over and over with different numbers.
- The result will always be 4, 2 or 1, whether using even or odd numbers.

## math magic trick

This time we are going to play with the number 37037:

- Multiply the number 37037 by a multiple number from 3 to 27.
- The result will always show figures with six equal digits (for example, 111111 if we multiply the original number by 3).

## Prediction of 10

Follow the following steps to surprise your friends with predictions with the number 10 as a result:

- Tell someone to tell you any number.
- Add 5.
- Subtract 2.
- Add 6.
- Subtract the original number.
- Add 1.
- The result is always… 10!

## Guess the birthday

Now you can guess your friends' birthdays (if you don't already know) through a clever mathematical trick with your calculator; Give the calculator to the person you want to surprise and tell them to follow the following steps:

- Enter the number 7.
- Multiply it by the birth month number (for example, March, 3).
- Subtract 1.
- Multiply the result by 13.
- Add the number of the day of your birth (numerical calendar day).
- Add 3.
- Multiply the result by 11.
- Subtract the month of your birth.
- Subtract the day of your birth.
- Divide the result by 10.
- Add 11.
- And finally, divide the result by 100.

Thus, a figure will appear on the calculator screen that will correspond to the birthday of the person we want to surprise; Thus, if you were born on March 2, the number 3.02 will appear, or what is the same, 3 (March), 02 (day of the month).

## Predicts bad luck

- Ask someone to enter a three-digit number twice into a calculator without you knowing (for example, 123123).
- Tell him that this number is divisible by 11; ask him to perform the operation.
- Now tell him that said number is also divisible by 13; ask him to perform the operation again.
- Tell him to divide the result by the original three-digit number.
- Tell him that the result is 7.
- If you want to predict bad luck, ask him to divide the number from step three by 7.
- The result will be 13, that is, the unlucky number.

## Infinite loop

- Ask someone to choose a number between 1 and 9.
- Ask the person who chose the number to multiply it by 9 and the result by 12345679 (omitting the 8 from the sequence) with the calculator.
- Ask the person who did the calculation with the calculator to tell you the result.
- Tell him the number you originally selected.
- The result will always show the original number repeated in sequence of XXXXXXXXXX.

## The mysterious cycle 6174

Now we are going to try our luck with the digit 6174, something that will surprise everyone and that really does not present a clear pattern. To play!

- Enter a four-digit number (not a multiple of 1111) into the calculator.
- First enter them in ascending order.
- Then do the same downwards.
- Subtract the small number from the large number.
- Repeat steps 2, 3 and 4 with the different results.
- It will always result in 6174!

## Extra trick: Delete digits on the iPhone calculator!

The calculator **iPhone** it does not allow **delete digits entered in calculator** independently through the touch keys on the screen; If we make a mistake in an operation, we must delete all the numbers and try again. That was until now! And a user discovered (and shared on networks, going viral) yes **we touch or slide our finger on the numerical screen** iPhone calculator app **deletes the last number entered**, something that does not appear in the official iPhone instructions. A very useful trick that many **iOS users** they don't know.