In primary school mathematics teaching,
With the help of fingers,
Visualize some abstract mathematical knowledge,
Intuition,
Students are easy to understand and remember.
One. One factor is that
nine
Multiplication calculation of
1
A clever memory
nine
Multiplication formula of
The multiplication formula is the key and difficult point in the teaching of lower grades.
It is difficult for students to understand and remember,
If you skillfully use your fingers to teach, the effect is good.
The specific method is as follows:
Hands together and straight,
Palm to yourself,
Starting from the left, each finger represents a slave
1
Until/very
10
quantity
Words. Bend the first to ninth fingers from left to right, indicating
nine
Multiply the product by several times (the hand index on the left side of the bent finger represents ten of the product)
A number, the right index finger represents a number of products)
For example, if you bend the sixth finger, you can see that there are five fingers on the left and four fingers on the right, then the product is
be
54
, which is 6954.
2
Clever calculation
nine
Multiply by two digits (one digit is the same as ten digits)
The method of sticking out your finger is the same as before. The difference is that the hand index on the left side of the bending finger represents the hundredth digit of the product, while the hand index on the right side represents the hundredth digit of the product.
The exponent represents one digit of the product, and the ten digits of the product add one.
nine
such as
449
Bend the fourth finger and there are three fingers on the left, indicating that the hundredth product is
three
; There are six fingers on the right, representing products.
The unit is
six
; Then write one on the ten digits of the product.
nine
, namely
449=396
three
Clever calculation
nine
Multiply by multiple numbers (all numbers are the same)
As can be seen from the foregoing,
nine
When multiplying by two digits, add one in the middle of the product.
nine
, therefore
nine
When multiplying by multiple numbers (each number is the same),
Intermediate product supplement
nine
The number of is: the number of digits of multiple digits-
1
such as
88889
Bend the eighth finger and there are seven fingers on the left, indicating that the highest position of the product is
seven
; There are two fingers on the right, indicating
The unit of the product is
2
; Intermediate product supplement
nine
The number of is:
four
-
1=3
, so
88889=79992