Clever calculation and fast calculation method in mathematics

First, a method of multi-bit multiplication that is not vertical. We can all calculate 1X 1 orally.

10X 1, but 1 1X 12.

12X 13

12X 14?

At this time, everyone usually uses vertical type. Through vertical calculation, the numbers are 132, 156, 168. Among them, the interesting rule is: the product is in one place.

A number is exactly the product of two factors and a number. Ten digits is the sum of two digits. The percentile is twice as much as ten.

The product of numbers. For example:

12X 14= 168

1= 1X 1

6=2+4

8=2X4

What if there is a carry? This law also applies to the carry case. When it is vertical, it will move to the next place as long as it is full.

~ For example:

14X 16=224

4=4X6 bits

2=2+4+6

2= 1+ 1X 1

Try to do the following questions:

12X 15=

1 1X 13=

15X 18=

17X 19=

Second, a fast calculation method of multiplying several eleven by several eleven

For example:

2 1×6 1=

4 1×9 1=

5 1×6 1=

8 1×9 1=

4 1×5 1=

4 1×8 1=

7 1×8 1=

What are the characteristics of these formulas? It is the multiplication formula of "several eleven times several eleven". We can use it like this: write the product of ten digits first, and then write the ten digits.

And (and full 10

Enter 1) and write a bit product. "Write ten products first, then ten sums (fill up 10.

1), write a little product "and have a look.

Multiplication formula of dozens of eleven times dozens of eleven. If the sum of ten digits is one digit, let's write the product of ten digits first, and then write ten digits.

Finally written as 1.

Must be correct; If the sum of ten digits is two digits, then we can directly write the product of ten digits plus 1.

Then write ten.

Single digit of the sum of digits, and finally write a 1.

It must be correct.

Let's look at two formulas:

2 1×6 1=

4 1×9 1=

Write the product of ten digits first, and then write the sum of ten digits (the sum is greater than 10).

Enter 1) and write a bit product. This fast calculation method directly writes out the thinking process when counting.

The first formula, 2 1× 6 1 =? The thinking process is: 2× 6 = 12, 2+6 = 8,

2 1×6 1