They can be a good way to have fun with the numbers, although the teachers consulted have their reservations about the way they are used in the school environment. If you want to surprise someone with a mathematical trick, here are some options. Do you know any other?
5 simple math tricks that will make you look like a genius 5 simple math tricks that will make you look like a genius
What did a number 3 say to a number 30? “To be like me, you have to be honest”.
Many times math can be heavy and difficult to understand.
But others, like in the opening joke (although it may seem bad to you) can be funny, even fun.
You can read: What is the utility of mathematics in everyday life
So at BBC Mundo we decided to put the magnifying glass on mathematical tricks. Those who can leave their interlocutor with their mouths open, because it seems that you would have worked magic to know the answer.
Some teachers of mathematics consulted think that they should be careful with them, especially in the school environment, while others think that it is a good way to motivate.
“We use tricks from time to time in the classroom, but mostly because we want to investigate how students work with them,” says David Wees, a Canadian mathematics teacher.
“I do not recommend teachers 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 BBC Mundo.
Meanwhile, Mexican mathematics professor José Andalón Estrada, founder of the Math2me site, says that “these mathematical entertainments motivate users.”
Here are five math tricks in case you want to try them out. Pick up pencil and paper or be encouraged to do it mentally.
1-The answer is always … 2
Let’s start with an easy trick.
Choose a number
Multiply it by 3
Divide that result by 3
Subtract the number you originally chose
Which it was the result? 2
2-The key number is 37
Think of a number with three equal digits. It can be any one from 1 to 9. Examples: 222, 555, 999.
Add the digits.
Divide the original number by the result of the sum from the previous step.
What did you get? 37
3-Divisible by 9
Choose a multi-digit number
Write it on 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 learning in high school algebra, but investigating whether or not it works could be done as soon as students learn to divide,” explains Professor Wees.
4. Multiply by 6
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 by which you multiplied and the number located in the ten will be half the number of the units. For example: 6 x 8 = 48
This is a little more complex, but you will guess the result no matter what numbers the other person chooses.
Select a 5-digit number, but the first must be a 2. Write it down and put it in a pocket.
Then write another 4-digit number on paper, for example 5735.
Ask the person with you to suggest another 4-digit number. For example it will say 8307. Write it below the number that you proposed in the previous step.
Then you choose another 4-digit number: 1692
Ask the person again to suggest another 4-digit random number, for example 8264
Finally you put another 4 digit number underneath: 1735
Add the five numbers. And the result is 25733. Check your pocket. Is it the same number? Surprised
Remember you have to build the 5 digit key number with number 2 at the beginning. That’s the one he keeps in his pocket, for example 25733.
When proposing the first four-digit number it has to have a certain particularity. It must start with the 3 central numbers, that is, 573 and the last digit must also be the last of its key number plus 2. So it would be 3 + 2 = 5. The first number he will propose will be 5735.
The number your partner chooses is random.
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But which one you select immediately afterward depends on the number he chose. And each digit must complete 9. That is, if you opted for 8307, you should 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 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 up all the figures and the result will be the number of the paper in your pocket.
Was it difficult for you?
Types of tricks
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, 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, Mexican mathematics teacher José Andalón Estrada, founder of the Math2me site, with thousands of videos on mathematics and 1.3 million subscribers, acknowledges that in his years in front of the class he never used this type of exercise, but he did He used logic problems and other types of activities to try to motivate the students.