First, every minute.
1. There are three hands on the clock face. They are hour hand, minute hand and second hand. The second hand is the fastest and the hour hand is the slowest. The hour hand is the shortest and the second hand is the longest.
2. There are 12 numbers on the clock face, 12 large squares and 60 small squares; There are 1 large cells between every two numbers, that is, 5 small cells.
3. Clockwise 1 grid is 1 hour; It takes 5 minutes to walk the minute hand 1 and the minute hand 1. It takes five seconds for the second hand to go 1. Go 1.
4. The minute hand goes 1, the second hand just goes 1, and the second hand goes 1 60 seconds, which is 1 minute.
5. The clockwise direction from one number to the next is 1 hour. It takes five minutes for the minute hand to turn from one number to the next. It takes five seconds for the second hand to turn from one number to the next.
6. formula. (The advance rate between every two adjacent time units is 60)
1 =60 points; 1 =60 seconds; 60 points =1;
7. Common time units: hours, minutes, seconds, years, months, days, centuries, etc.
1 century = 100 years, 1 year = 12 months.
Second, a preliminary understanding of music score
1, fraction: divide an object or a graph into several parts on average, and each part is its fraction. Score: divide an object or figure into several parts, and take a few parts, which is the score of the object or figure.
2. The more shares a whole is divided equally, the smaller the number each share represents.
3. The method of comparing sizes:
The numerator of (1) is the same, but the fraction with small denominator is large, and the fraction with large denominator is small. (2) The denominator is the same, the numerator is large, and the numerator is small.
4. Fraction addition and subtraction: ① Calculation method of same denominator fraction addition and subtraction: same denominator fraction addition and subtraction, same denominator fraction addition and subtraction, and same numerator fraction addition and subtraction. (2) How many fractions to subtract from 1: When calculating how many fractions to subtract from 1, first write1as a fraction with the same denominator as the subtraction, and then calculate.
5. The meaning of score: divide a whole into several parts on average, which means that several parts are the score of the whole, the number of parts divided is the denominator, and the number of parts taken is the numerator.
6. How to calculate that one number is a fraction of another number: first divide this number by the denominator (find out the number of copies of 1), and then use the quotient multiplier (find out what they are).
Third, measure
1. In daily life, relatively few items can be used as units (millimeters, centimeters, decimeters); Large objects are usually measured in meters; Generally, the unit for measuring long distances is (km), also called (km).
2. 1 The thickness of coins, rulers, magnetic cards, buttons and keys 1 min is about1mm..
3. When calculating the length, you can only add or subtract the same length unit.
4. The relationship between length units is as follows: (the propulsion rate between every two adjacent length units is 10).
① the propulsion rate is 10: 1 m = 10 decimeter, 1 decimeter = 10 cm, 10 mm,10 mm.
② The advancing speed is 1 00:1m =100 cm,1decimeter = 100 mm, 100 cm = 1 m,/kloc-0.
③ The forward speed is1000:1km =1000 m,1km = 1000m = 1km.
When we express the weight of an object, we usually use (mass unit). In life, the weight of lighter items can be measured in grams. According to the quality of general goods, it is usually a unit (kg); Measure the mass of heavy or bulk goods, usually in tons.
6. The ratio of two adjacent mass units is 1000.
1 ton = 1 000kg/kg = 1 000g1000kg = 1 ton1000g =1kg.
Fourth, addition and subtraction within 10,000.
1, read and write (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.
2. 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: Look at the last digit. If it is 0-4, use the four-shed method. If it's 5-9, use the decimal method.
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, subtract 1 from the last digit and add10 to the standard; If the previous digit is 0, it is 1 of the previous digit.
Fifth, double understanding.
Meaning of 1 and multiples: To know the relationship between two numbers, first determine who is the multiple of 1, and then compare it with another number. There are several multiples of 1 in another number.
2. How to find how many times one number is another number: one number ÷ another number = multiple of 3? How to find how many times a number is this number × multiple = multiple of this number?
Six, rectangle and square
1. A closed figure with four straight sides and four corners is called a quadrilateral.
2. Features of quadrilateral: It has four straight sides and four corners.
3, the characteristics of the rectangle: the rectangle has two lengths and two widths, the four corners are right angles, and the opposite sides are equal.
4. Characteristics of a square: it has four right angles and four equal sides.
5. Rectangular and square are special parallelograms.
6. Features of parallelogram: ① The opposite sides are equal and the diagonals are equal. ② Parallelogram is easy to deform. (Triangle is not easy to deform) 7. The length of a closed figure is its circumference.
8. Formula: rectangle perimeter = (length+width) ×2 or length ×2+ width×2 rectangle length = perimeter ÷2- wide rectangle width = perimeter ÷2- long square perimeter = side length ×4 square side length = perimeter ÷4.
Seven, multiple digits by one digit
1, estimated. (Find the approximate multiple digits first, and then calculate. Such as 497×7≈3500)
2、
① Multiply 0 with any number to get 0;
② Multiply 1 by any number other than 0 to get the original number.
3. Three digits times one digit: the product may be three digits or four digits.
4, multiple digits multiplied by one digit (carry) written calculation method:
For the alignment of the same digit, multiply the single digit by one digit, and multiply the digits on each digit of the multi-digit by one digit respectively. If the product of the best digits is more than several tens, it will go to the previous digit, and if it is multiplied by which digit, the product will be written below which digit.
5. Multiply by 0 in the middle of the factor:
(2) There is a 0 in the middle of the factor, and the number on each bit of the multi-digit is multiplied by one digit. When multiplying with the middle 0, if it is not followed by a number, this bit will be occupied by a 0, and if it is followed by a number, it must be added.
6. Simple calculation of multiplication with 0 at the end of a factor: When calculating with a pen, you can align one digit with the number before the multi-digit 0, then see how many zeros are at the end of the multi-digit and add several zeros at the end of the product.
7. (About Approximation) Application problem: If there are "approximation", "approximation", "estimation" and "estimation" in the problem, estimation is used regardless of whether there is approximation in the conditions. →(≈)
8, subtraction calculation method:
① Subtract the difference from the minuend to see if the result is equal to the minuend.
② Add and subtract numbers with the difference to see if the result is equal to the minuend.
9. Calculation method of addition:
① Exchange the positions of two addends and recalculate.
② Add and subtract one addend to see if the result is equal to another addend.