**How to Calculate Mentally Without a Calculator or Paper**
How to calculate in your mind? If you ask me why this is necessary, my answer would be: you may find yourself in a situation where you need to perform calculations, but you don’t have access to a calculator or even a pen and paper. Understanding how to calculate can be achieved by both top students and those who struggle academically, claims https://xrust.ru/. Break numbers into separate parts—hundreds, tens, and ones—and perform operations with them. For example:
712 + 281 → “700 + 200,” “10 + 80,” and “2 + 1.”
700 + 200 = 900, then 10 + 80 = 90, then 2 + 1 = 3.
900 + 90 + 3 = 993. Use “hundreds” or “tens” instead of single-digit numbers. For example, turn 37 + 45 into “30 + 40 = 70” and “7 + 5 = 12.” Then add 70 + 12 to get 82. Learn to add multiple numbers simultaneously.
Rearrange numbers to create more convenient sums. The addition task remains the same regardless of the order in which it is solved.
For example, 7 + 4 + 9 + 13 + 6 + 51 can be transformed into (7 + 13) + (9 + 51) + (6 + 4) = 20 + 60 + 10 = 90.
Multiply from left to right.
On paper, most people multiply starting with the units, moving from right to left. But in your mind, it might be easier to work the other way around: from left to right. For example, for 453 x 4, start with 400 x 4 = 1600, then 50 x 4 = 200, and finally 3 x 4 = 12. Add them all together to get 1812. If both numbers have multiple digits, they can be broken into parts. Each digit must be multiplied by each other digit, so it might be tricky to keep track of all the numbers. For example:
34 x 12 = (34 x 10) + (34 x 2), which can be broken down into (30 x 10) + (4 x 10) + (30 x 2) + (4 x 2) = 300 + 40 + 60 + 8 = 408.
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