I. Reading and writing numbers
/kloc-a number between 0/and 20
Ordinal number: from small to large 01234567891121314151665438.
Countdown: in descending order: 20 19 18 17. ...
Singular: 1, 3, 5, 7, 9 ...
Even numbers: 2, 4, 6, 8, 10 ...
(Note: 0 is neither singular nor even, and 0 is even. Odd and even numbers are said in life, and even numbers are said in mathematics. )
2. Two digits
(1) We often meet ten objects as a whole in our life. In fact, ten "1" is one "10" and one "10" is ten "1".
For example, there are (1) tens and (1) ones in a:1;
1 1 has one (1 1).
12 has (1) tens and (2) ones;
12 has (12) 1, 13 has (1) 10 and (3)1;
13 has (13) 1, 14 has (1) 10 and (4)1;
14 has (14) 1, 15 has (1) 10 and (5)1;
15 contains one (15) ...
19 has (1) tens and (9) ones;
In other words, there are (19) 1 in 19 and (2)10 in 20;
There are (20) in 20. B: Look at the number board (1 1~20) and say that the numbers on the board are composed of ten and one.
(2) On the counter, what is the first number from the right? What's the second place? (10) What does 1 bead mean? (stands for 1 one) What does the tenth 1 bead mean? (for 1 10)
(3) Read 1 1, 12, 13, 14, 15, 16, 17,/kloc.
For example: 14, read: 14 and write: 14. The unit digit is 4, which means 4 1, and the tenth digit is 1, which means 1 piece 10.
Second, compare size and quantity.
1, arrange digital dolls.
5, 6, 10, 3, 20 and 17 can be arranged in the order from largest to smallest, or in the order from smallest to largest.
Pay attention to write a number when doing the problem, cross out one, don't be heavy, don't miss it. )
2, take any two numbers within 20, and you can use who is bigger than who or who is stronger than who.
For example, 16 is greater than 15, which means 16 > 159 is less than 13, which means 9 < 13.
3. Usage of "Bi"
Look who is behind the word "Bi". If it is greater than 1, add 1 to the number; if it is less than 1, subtract 1 from the number.
For example, the number 2 less than 5 is (3), and the number 3 greater than 4 is (7).
3. What number and what number?
Look at the picture. How many numbers are there? (16 number) What's the number on the left? What's the number on the right? Circle the left three; Circle the second one on the right.
(When reviewing this kind of knowledge, we should distinguish between left and right and determine the direction at the same time; Know the difference between a few and a few. )
Fourth, the adjacent number
2 is preceded by 1 and followed by 3. 2 plus 1 equals 3, 3 minus 1 equals 2. The numbers adjacent to 2 are 1 and 3.
3 is preceded by 2, and 3 is followed by 4. If you add 1 to 3, it is 4. If you divide 4 by 1, it is 3, and the numbers adjacent to 3 are 2 and 4.
20 is preceded by 19 and followed by 2 1 ... The adjacent numbers are 19 and 2 1.
Five, the contrast of things
1. Comparison of two things
To compare the size, quantity, length, height and weight of two things, we should take one of them as a reference or one of them as a standard, and then compare them, so that we can say that the other thing is bigger or smaller than the standard, more or less.
Comparison length: The commonly used methods should be aligned at one end, multi-grid comparison or symmetrical comparison.
Height: Pay attention to the contrast on the same plane.
How much to compare: apply the principle of one-to-one correspondence.
2. Comparison of three things
You can compare them first. Then, according to the comparison results, the conclusion of three things comparison is drawn.
If A is heavier than B and B, then A is heavier than C. A is the heaviest and C is the lightest.
A is heavier than B, A is heavier than C, only A is the heaviest, and we have to compare B and C to know who is the lightest.
Six, addition and subtraction (a)
Add up two numbers.
Appendix+Appendix = and: 3+ 13= 16, where 3 and 13 are addends and the sum is 16.
Take a part from a number and find out how much is left. Subtract.
Minus-Minus = Difference: 19-6= 13, where 19 is the minuend, 6 is the subtraction, and the difference is 13.