Gizmodo in Spanish presents five techniques to improve our mental ability to solve arithmetic equations and not be embarrassed when we have to divide the bill or the dinner tip with our friends:
- Addition and subtraction from left to right. We were taught to do it the other way around, which makes a lot of sense with paper and pencil, but starting with the high numbers is more intuitive for mental calculation and will help you break down the problem. Thus, if you have to add 58 + 26, calculate 50 + 20 = 70 and 8 + 6 = 14. Finally, all that remains is to calculate 70 + 14 = 84.
- Simplify the problem by temporarily changing some values. For example, if you need to calculate 593 + 680, add 7 to 593 so that it becomes 600, which is a more manageable number. Calculate 600 + 680 = 1280 and don’t forget to subtract the 7 you added before. The result is 1273. You can do the same with multiplication: for 89 x 6, calculate 90 x 6 and then subtract the remaining 6. 540 – 6 = 534.
- Break down the big problem into several small problems. For example, multiplying a number by eight is equivalent to doubling it three times, so to calculate 12 x 8 you can double twelve three times: 24, 48, 96. If you want to multiply by 5, first multiply by 10 and then divide by 2, which is usually easier. In this case, if you have to calculate 18 x 5 you would do 18 x 10 = 180 and then 180 / 2 = 90.
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General editor and co-founder of .com. I specialize in the clinical care of adults with problems of depression, anxiety and emotional dysregulation.