1, two meanings of multiplication: what is the sum of several; What is the sum of several?

2. Three meanings of division: expression: divide a number into several parts, and each part is a few (the meaning of average division); Representation: how many digits a number has (including the meaning of division); Representation: One number is several times of another number (the meaning of multiple division).

Find out how many times one number is another number, and then divide it.

4. Know that one number is several times that of another number, and find a number by multiplication.

5. Know that one number is several times that of another number, and find another number by division.

6. Find the multiple of a number by multiplication.

7. Equitable formula: total number ÷ number of copies = number of copies.

8. Formula including division: total number ÷ number of copies = number of copies.

9. Be familiar with the names of all parts of multiplication and division and the reading of formulas.

Example: 3× 4 = 12 multiplier product (read: 3 times 4 equals 12. Example: 12 ÷ 4 = 3 Divider quotient of divisor sign (read: 12 divided by 4 equals 3. )

10, on the map, it is generally up north, down south, left west, right east.

1 1. If facing east, the back is west, the left is north, and the right is south. If facing west, the back is east, the left is south and the right is north. If you face south, your back is north, your left is east and your right is west.

12, 1 =60 minutes, 1 minute =60 seconds.

13, elapsed time = end time-start time: start time = end time-elapsed time; End time = start time+elapsed time.

14, the common time unit is sometimes, minutes and seconds.

15. There are 12 big squares and 60 small squares on the clock. It takes 1 hour to walk a big square in an hour hand, 1 minute to walk a Little Square in a minute hand and 5 minutes to walk a big square in a minute hand.

16. In the division formula with remainder, the remainder must be less than the divisor.

17. According to the relationship between the parts of division, several formulas can be derived: dividend = divisor × quotient+remainder; Divider = (dividend-remainder) ÷ quotient; Quotient = (dividend-remainder) divider; Remainder = dividend divided by quotient.

18, in the formula without brackets, there are addition and subtraction and multiplication and division. Calculate multiplication and division first, then add and subtract. If there is only addition and subtraction or only multiplication and division, it should be calculated from left to right. Formulas in brackets should be calculated first.

19. We usually refer to all directions as "East, West, South, North, Southeast, Northeast, Southwest and Northwest".

20, 10 One thousand is ten thousand; 10 One hundred is one thousand; 10 Ten is one hundred. 2 1. From the right, the first place is the unit, the second place is ten, the third place is one hundred, the fourth place is one thousand, and the fifth place is ten thousand.

22. Pay attention when reading: No matter how many zeros there are at the end, there are one or more zeros in the middle, and read only one zero. Note when writing numbers: there is nothing on any number, just fill in a zero placeholder on that number.

23. When comparing figures, it should be noted that the figures with more digits are greater than those with fewer digits; When the number of digits is the same, the number with the highest digit is greater than that with the highest digit; When the highest digit is the same, the ratio of one digit to another digit in descending order, which digit is larger, indicates that the number is larger.

24. When reading, read from the (highest) position in order (from high to low).

25. Length units: kilometers, meters, decimeters, centimeters and millimeters. Expressed in letters: km, m, dm, cm, mm.

26. The advance rate between commonly used "adjacent" length units is "10", the advance rate between "separated" 1 00 "and the advance rate between two" separated "length units is" 1000 ". We also derived seven unit conversion formulas, namely:

1m = 10 decimeter 1m = 10 decimeter; 1 decimeter = 1 0cm1decimeter =10cm; 1cm = 10mm 1cm = 10mm； 1m = 100cm 1m = 100cm； 1 decimeter = 100 mm 1 decimeter = 100 mm; 1m = 1000mm 1m = 1000mm； 1 km = 1 000m1km =1000m.

27. We also know that there are (10) cells in 1cm, and the length of each cell is1mm. 1 decimeter is about the length of a palm. 1 cent coins are about 1 mm thick. When long distance is expressed, it is expressed in "kilometers".

28. Written calculation method of three-digit addition (carry addition): the same digits are aligned; Start from the unit; Whoever reaches 10 will be promoted to 1.

29. Written calculation method of three-digit subtraction (abdication subtraction): the same number is aligned; Reduce from the unit; Which one is not enough to reduce, borrow a 1, this one is added with 10 and then reduced.

When estimating in this unit, the number can be regarded as an integer or an integer, so that the estimated answer will be closer to the actual answer.

3 1. We can check whether the result is right or wrong.