1, east-west relative, north-south relative.
2. In the morning, the sun is in the east, facing the sun. The front is east, the back is west, the left is north and the right is south.
In the afternoon, the sun is in the west, and we face the sun. The west is in front, the east is behind, the south is on the left and the north is on the right.
4. Maps are usually drawn from north to south, left to west and right to east.
Compass can help us to identify the direction.
6. We need to know eight directions, and we can describe the location of the place according to the schematic diagram given. Usually, the southeast lies between the east and the south. The northeast is between east and north. Between the west and the south is the southwest, and between the west and the north is the northwest.
7. Divide 0 by any number that is not 0 to get 0. Multiply 8,0 by any number, and you get 0.
Note: In the division formula, 0 cannot be divided.
The estimate of multiplication and division must be. Use the 4-to-5 method.
Such as multiplication estimation: 8 1×68≈5600, that is, 8 1 is estimated to be 80, 68 is estimated to be 70, and 80 times 70 is 5600. Division estimation: 493÷8≈60, that is, 493 is estimated as 480(480 is a multiple of 8, which is also the most closely related to 492), and then 480÷8 is calculated to get 60.
Can correctly calculate the two-digit number multiplied by the two-digit number, such as: 57× 89; Can accurately calculate the divisor's one-digit division, such as: 4 17÷4, and will use multiplication to check, dividend = divisor × quotient+remainder.
Divide three digits by one digit. If the hundred digits are greater than the divisor, the quotient is three digits. If the hundred digits are less than the divisor, the quotient is two digits. The remainder is less than the divisor.
9. There are 12 months in a year; There are four quarters in a year. (1, February and March are 1 quarter; April, May and June are the second quarter; July, August and September are the third quarter; 10, 1 1 and 65438+February are the fourth quarter)
10, the method of recording the month: 1, 3, 5, 7, 8, 10, wax, 3 1 day is not bad; 4: 00, 6: 00, 9: 00 and 30: 00 in winter, only in February.
1 1. A normal year has 365 days, 28 days in February, 18 1 day in the first half and 184 days in the second half. The normal year is 52 weeks, 1 day.
12. There are 366 days in leap year, 29 days in February, 182 days in the first half and 184 days in the second half. A leap year has 52 weeks and 2 days.
13, the Gregorian calendar year is a multiple of 4, usually a leap year; However, the Gregorian calendar year is a whole hundred, and it must be a multiple of 400 to be considered as a leap year.
14, year, month, day, hour and minute are all time units.
15. The hands on the clock go twice a day.
Circle, ***24 hours. Therefore, the timing method of 0:00-24:00 is often used, which is usually called 24-hour timing method. The timing method from 1 to 12 is called ordinary timing method. 16, 1 day (day) =24 hours 1 hour =60 minutes 1 minute =60 seconds.
17. A man is 20 years old, but he has only had five birthdays. He was born on February 29th. Because there are only 29 days in leap year and no 29 days in normal year, there is no birthday every year.
18, the anniversary is calculated by subtracting the original year from the current year to get the anniversary.
Note: To correctly distinguish between a normal year and a leap year, we should know that every four years is a leap year, and every hundred years is a leap year of 400 years. Will ask about the elapsed time. For example, how long does it take for a car to leave at 8: 20 in the morning and arrive at the finish line at 5: 50 in the afternoon? The first step is to convert 5: 50 pm into 24-hour time method, with 5: 50+ 12 = 17: 50, and the second step is to calculate the elapsed time with 17: 50 -8: 20 =9: 30.
19, the size of the surface or closed figure of an object is their area.
20, compare the size of the two graphics area, to use a unified area unit to measure.