How to learn quickly take ?
It would seem that anyone in our time of modern technology you need this skill?After all, you can always take a calculator, which is available in any mobile phone, and to make the necessary calculations.However, sometimes the desired device can not be there.Then it has a useful ability to quickly take in mind.
There is a certain set of arithmetic algorithms, each of which in a given case, can significantly ease the bill.Start learning fast count in his mind it is necessary to memorization of algorithms.
Subtraction 7, 8, 9
If you need to subtract from any number of 9, 8 or 7, subtract 10 from it, and then add 1, 2 or 3, respectively.For example: 52-9 = 52-10 + 1 = 43.
Multiplication by 9
To multiply any number by 9, multiply it first by 10, that is, just add a zero at the end, and then subtract the first multiplier from the result (ie, the number that is multiplied).
For example, 72 * 10 (= 720) - 72 = 648.
Multiplication and division by 2
This seemingly very simple operation, but when it comes to large numbers, everything becomes difficult.Particularly problematic to multiply the number of non-circular.150 multiplied by two very simple, but the 146 is much more difficult.In this case, we rounded 146 to 150, multiply, and then subtract the difference from the result rounded and unrounded numbers multiplied by two.That is:
- 150 * 2 (= 300) - 4 * 2 = 292.
Similarly to arrive and when divided:
- 150/2 = 75
- 75-4 / 2 = 67.
division and multiplication by 4 and 8
division and multiplication by 4 and 8 - are, respectively, double and quadruple division and multiplication by two, so that these actions perform better consistently.That is: 16 * 16 * 4 = 2 (= 32) * 2 = 64.
Multiply by 5 and 25
To quickly multiply by five, multiply the number by 10, then divide in half.For example: 5 = 25 * 25 * 10 (= 250) / 2 = 125.
25 To multiply, divide the number by four, and then multiply it by 100. For example: 16 * 25 = 16/4 (= 4)* 100 = 400.
multiplication by single digits
to quickly multiply the number by any-one, it is convenient to perform sequential multiplication.For example: 84 * 8 = 80 * 8 (640) + 4 * 8 (32) = 672
or 153 * 6 = 100 * 6 (600) + 50 * 6 (300) + 3 * 6 (18) = 918.
of course, at first glance, these algorithms may seem too zamorochennye addition, you can even think that some of the actions you can perform much faster without using them.However, this is only until such time as your actions according to the algorithm will not be brought to automatism.
More lessons can be found here - 4brain.ru.Also, read more in our article How to learn to count.