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Super 11 rule
There is a strong likelihood that many people know 10 rule. That is, when you multiply the number by 10, you add 0 at the end of the number. However, rule 11 may be known to many. It is so easy to understand
-. As you multiply any two-digit number of 11
– Take 36 in this example (3-6) and take a gap between them.
– The sum of two numbers, 3 and 6 together
-. Place the result, 9 of the gap between
– It is simply done 39 x 11 = 3 96
However, there is one tricky thing you should remember, if the result after you have added two places is more than9, put only numbers representing the “ones” in the gap. For example:
… 74×11 7_4 …. 4 + 7 = 11 …
Add one gap, and add 1 to 7 to obtain 8, the answer to 74 x 11 = 814
How to multiply by 999, 99 or 9
Multiply the number of 9 is just like multiplying it by 10-1.
As such, multiply 9 × 9 is9 (10-1) will determine the outcome of 90 -9 = 81
Another example:
9 × 68 = 68 … 01/10)
= 680-68
= 612
To multiply the number by 99 is the same as the (100-1)
47 multiplied by 99 …. 47 (100-1)
= 4700-47 = 4653 …
Multiply the number 1000 means the same as multiplying the same by (1000- 1)
Therefore 55 multiplied by 1000 is the same as…..55(1000-1)
=55000-55
=54945
How squ9are to two digit figures
Take, for example, you want to square 48. The first step is squaring each of the letters to get partial results.
4 × 4 and 8 × 16 8 = 64. Then put two numbers together, 1664.
From there, you should multiply the numbers the number you want to square …. 4 × 8 = 32
Double product to get 64
Add 64 to 1664 to get the answer
Math can be terrifying idea for many but with this cool mental math tricks and a little practice to perfect them, general knowledge and speed in mathematics will be considerably improved.
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