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*What did a number 3 say to a number 30? **” **To be like me, you have to be honest **. **“*

Many times mathematics can be heavy and difficult to understand.

But others, as in the joke at the beginning (although it may seem bad) can be funny, even fun.

For that reason, in Rava we decided to put the magnifying glass in the **mathematical tricks** . Those that can leave your interlocutor with their mouths open, because it seems that you would have done **magic to ****know ****the answer.**

Some teachers of mathematics consulted think that we must be careful with them, especially in the school environment, while others think it is a good way to motivate.

“From time to time we use tricks in the classroom, but mostly because we want to investigate how students work with them,” says David Wees, a Canadian professor of mathematics.

**“I do not recommend ****teachers ****to use tricks without an explanation of why they work** , or without emphasizing the ability of students to discover for themselves what is behind them,” he tells.

Meanwhile, Mexican mathematics professor José Andalón Estrada, founder of the *Math2me* site , says that “these mathematical entertainments motivate users.”

Here we leave you five mathematical tricks in case you want to try them. Take pencil and paper or encourage yourself to do them mentally.

Let’s start with an easy trick.

- Choose a number

- Multiply it by 3

- Add 6

- Divide that result by 3

- Subtract the number you chose in the beginning

Which it was the result? 2

- Think of a number of three identical digits. It can be anything from 1 to 9. Examples: 222, 555, 999.

- Add the digits

- Divide the original number by the result of the sum of the previous step.

What did you get? 37

Let’s see how it goes with this one.

- Select an even number from 1 to 9

- Multiply it by 6

- The result will end with the same digit for which you multiplied and the number located in the ten will be half the number of units.

For example: 6 x 8 = 48

- Choose a multi-digit number

- Write it in reverse

- Subtract this number with the first

- The result is always divisible by 9

For example: 36782 – 28763 = 8019 which is the same as 9 x 891.

“Proof of this only requires what was learned in algebra in high school, but researching whether it works or not could be done as soon as students learn to divide,” explains Professor Wees.

This is a bit more complex, but you will guess the result no matter what numbers the other person chooses.

- Select a 5-digit number, but the first number must be a 2. Write it down and put it in your pocket.

- Then, write another 4-digit number on paper, for example, 5735.

- Ask the person with you to propose another 4-digit number. For example, say 8307. Write it below the number you proposed in the previous step.

- Then you choose another 4-digit number: 1692

- You ask the person to propose another 4-digit random number, for example 8264

- Finally you place another 4-digit number below: 1735

- You add the five numbers. And the result is 25733. Check your pocket.
**It is the same number?**Surprised?

**The explanation**

Remember that you have to build the 5-digit key number with the number 2 at the beginning. That’s the one you keep in your pocket, for example 25733.

When you propose the first four-digit number, it has to have a certain peculiarity. It should start with the 3 central numbers, that is 573 and the last digit should also be the last of your key number plus 2. So it would be 3 + 2 = 5. The first number you will propose will be 5735.

The number that your partner chooses is random.

But the one you select immediately after depends on the number he chose. And each digit must complete 9. That is, if you chose 8307, you must write 1692 below because 8 + 1 = 9; 3 + 6 = 9; 0 + 9 = 9; 7 + 2 = 9.

The other person chooses the next number and you repeat the same procedure with yours by completing 9 in each digit. That is, if your partner chose 8264, you write 1735. (8 + 1 = 9; 2 + 7 = 9; 6 + 3 = 9; 4 + 5 = 9)

At the end, add all the figures and the result will be the paper number in your pocket.

According to the teachers consulted, there are two kinds of mathematical tricks.

On the one hand there are those that eliminate some mathematical thoughts for the students in order to facilitate the resolution of a problem.

And on the other hand, those that are the result of a deep mathematical idea that is often not completely obvious to the person who uses the trick.

But Professor Wees insists that he would **not share a trick with the students unless he was ****” ****sure they ****understand ****why it works.”**

For his part, the Mexican mathematics professor José Andalón Estrada, founder of the site *Math2me* , with thousands of videos on mathematics and 1.3 million subscribers, recognizes that in his years in front of the class he never used this type of exercises, but he did He used logic problems and other types of activities to try to motivate the students.

However, in the YouTube channel the audience is different, he says.

“People mostly come to entertain themselves, but we can capture the attention of those students who do not know they can study on the internet , which is why we started using **‘edutainment’** , which is the educational combination with entertainment,” he says. BBC World.

“That’s where the idea of publishing tricks came from and maybe people who did not want to see mathematics indirectly are doing it,” he continues.

“We are proving that there are people who are interested in. It is very important to attract young people to science”.

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