There are no more traumatic school exercises for children than those dealing with mental math: adding, subtracting, multiplying and dividing. It is something that is also heavy for parents, who cannot find the method to teach their children. I have to admit that it was also, is and will be a problem for the writer, that is why this article is a challenge to discover some mental math techniques to add and multiply quickly and that they can help us to acquire this ability without causing us many headaches.
An exercise that was quite difficult for me to do when I was in school was to perform chin-ups, because I had to lift my body - with more than ninety kilos - holding both my hands to a bar that was eight feet high. It was not even in case something very pleasant, as you can imagine, and less if a teacher was evaluating me expecting me to meet the minimum objective for the grade. I remember that as time went by, I realized different strategies that could help me to achieve my goal. In the end, between trial and error, I tried one or the other and managed to perform a happy test of strength and successfully.
I was reminded of that challenge when meeting another major: performing mental math operations. I don't know what it is and it was worse! This exercise did not hurt my biceps, but the mental pain trying to solve the odd operation was incredible. Well, just as it was with that sports test, I set out to investigate some mental arithmetic techniques to add and multiply quickly, and this is what I found:
1. When two pairs of numbers are added to which only one unit separates… (18 + 20, 34 + 36) The result is equal to twice the pair that is skipped… (19 × 2 = 38, 35 × 2 = 70).
2. If the numbers added are consecutive, double the lowest figure is calculated and the result is added 1. Example: 56 + 57 = 56 × 2 + 1 = 113
3. However, the addition is easier if the first number is higher than the second, so it is appropriate to execute the exercise in this way. If we have to add 8 + 32, it will be easier to solve this sum backwards, that is, 32 + 8. In multiplication, it is convenient to do the same exercise.
4. When the numbers to be added have many digits, the idea is to separate the ones on the left, they are added and a zero is added to the result. If the number represents a ten, two zeros if it is a hundred and so on. Then the rest are added and, finally, the results of both operations. It is easier if we see the following example. Let's put the sum 789 + 123 and see step by step what to do ...
The first is like this… 7 + 1 = 8 (800). Then we do the next step… 89 + 23 = 112. Finally, the result would be the following ... 800 + 112 = 912.
5. In subtraction, the rounding technique works. When one of the numbers that is subtracted is almost a ten, that ten is subtracted and the missing figures are added to complete it: This is the operation… 94-29 Then… 94-30 + 1 = 65.
6. Rounding is also valid in multiplication. In this case, the operation would be calculated as follows. The operation would be 892 × 9 = 8.028. So… (800 + 92) x9 = 7,200 + 828 = 8,028.
These techniques have been developed by different active teachers, which invites other teachers and educators to develop our own strategies, to play with our own creativity, to challenge ourselves to find the tool that allows us to overcome these challenges and teach our students new paths to reach your goal.
Creativity also means investigating, investigating the entire wide world of the Internet and the different videos that are on the Internet to find tools or techniques that invite us to discover the one that suits the characteristics of each one.
And if we talk about research, there are methods that have spread in different cities. For example, in my country, Chile, the Singapore method or the Kumon method has become known, both of which have a whole apparatus that provides the development of these mathematical skills.
At the end of the day, apart from finding one or another technique, the important thing is to find the one that most closely resembles your own personality; that instead of choosing the one that makes it difficult for me, execute the one that best suits my own way of being. In the end, this is what this same research on different methodologies consists of, in finding oneself and that thanks to these means it can find its own integrality.
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