I round one of the numbers (usually the larger one but either one works) up or down to the nearest number that is easy to multiply in my head.
Like this:
423 x 12
Becomes:
425 x 12
Then I would say that if 425 x 12 = ___, then 850 x 6 = ____ too.
Because 850 = 425 x 2 and 6 = 12 / 2
And if 850 x 6 = ____, then 1700 X 3 = ____ also.
1700 x 3 = (1000 x 3) + (700 x 3) = 3000 + 2100 = 5100
So, 425 x 12 = 5100. But, we started with 423 not 425.
(425 x 12) - ((425-423) x 12) = 423 x 12
425 - 423 = 2
So, we need to multiply the difference (2) by 12 and subtract that from the 5100 to get the real answer.
2 x 12 = 24
5100 - 24 = 5100 - 25 + 1 = 5076
423 x 12 = 5076 Ta Da!
Another way, is to break one into easy to use numbers (12 is good for this) and skip the rounding step. But, sometimes there is no easy split (3746 x 5317) and then the rounding works better. But, here is the split method (I also used it above.)
423 x 12 = (423 x 10) + 423 x 2
423 x 10 = 4230 and 423 x 2 = 846
4230 + 846 = 5076
With practice you will get faster at this and you will even be able to hold a conversation while doing the math. Then everyone will think you are a genius!
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in school, i used multiplication in my planner,a print out or a calculator to help me know it
It's quite possible you're looking for the wrong symbol on the calculator to represent Multiplication. Instead of using the normal X sign, on a windows calculator, multiplication is represented by an asterisk - one of these -> * Multiplication exists on all Windows Calculators.
Use the method of long division.
99 squared, written 992, is the same as 99 x 99 (multiply the number with itself). You can simply do the multiplication.
By using long multiplication: multiply the given number by 35, then move the decimal point two places to the left. For example: what is 35% of 743? 743 x 35 ---------- 22290 3715 ---------- 26005 ~ 260.05 ----------