People's education edition: knowledge points of unit 2 of mathematics in the first volume of the third grade of primary school
1. Know the integer (memory: 10, one thousand is ten thousand) 2. Read and write numbers (write Chinese characters when reading and Arabic numerals when writing).
No matter whether there is a zero or several zeros at the end of a number, this zero will not be read.
② There is a zero or two consecutive zeros in the middle of a number, and both of them read only one zero.
3. Comparison of figures:
① Numbers with different digits are larger, and those with more digits are larger.
(2) Compare the sizes of numbers with the same number of digits. First, compare the numbers on the numbers of these two numbers. If two digits are the same, compare the next digit, and so on.
4. Find the approximate value of a number:
Memory: Look at the last digit. If it is 0-4, use the four-shed method. If it's 5-9, use the decimal method.
Its three digits are 999, the smallest three digits are 100, the fourth digits are 9999, and the smallest four digits are 1000.
The three digits of are less than the smallest four digits 1.
5, the minuend is a three-digit continuous abdication subtraction steps:
① When the columns are vertical, the same numbers must be aligned;
(2) When subtracting, which digit is not reduced enough will be1of the previous digit; If the previous digit is 0, it is 1 of the previous digit.
6. Pay attention to the middle 0 when doing the problem, because it is abdicated continuously, so you should retreat from one hundred to ten at 10, and then from ten to one at 10, and lend one, so there are only nine left in the ten, not 10. (Sum of two three digits: it may be three digits or four digits. )
7. minuend = minuend+difference
Sum = Addendum+Another Addendum
Subtraction = minuend-difference
Appendix = Sum-Another Addendum
Difference = minuend-minuend
People's education edition: unit 2 of mathematics in grade three of primary school
First, write the number directly. 12+45= 63-28= 15+40= 28+4 1=
800+500= 90-36= 52- 19= 500+700=
6000-4000= 1500-800=
Second, fill in.
1, 4 hundreds and 8 tens add up to (), and 25 tens are ().
There are 262 pear trees and 304 peach trees in the orchard. There are about () pear trees and peach trees, and there are about () fewer pear trees than peach trees.
3. There are 280 boys and 300 girls in Grade Three, and there are students in Grade One ().
4. Mom pays 52 yuan for electricity and 86 yuan for water. Paying the water bill costs () yuan more than paying the electricity bill.
Guangming Fruit Shop sold 420kg watermelon last week, 370kg this week, and () kg watermelon these two Mondays.
Third, even a company.
430+400 9 10-680
520-290 270+560
300+290 970- 150
1000- 180 390+200
Four. Fill in ">" in ○. "