I. Measurement:

(1) unit of length:

1 km = 1 000m1m = 10 decimeter.

1 decimeter = 1 0cm1cm =10mm

1 m = 10 decimeter =100 cm =1000 mm.

(2) Quality unit:

1 ton = 1 000kg1kg =1000g

Second, the addition and subtraction within ten thousand years:

(1) subtraction:

1, minuend-subtrahend = difference

2. subtraction = minuend-difference

3, the minuend = difference+subtraction

(2) Add:

1, addend+addend = sum

2, addend = and-addend

(3) addition and subtraction:

Check the calculation of addition:

1, exchange the position of the addend, the same.

2. Subtracting one addend from the sum equals another addend.

Check the calculation of subtraction:

1, plus or minus the difference equals the minuend.

2. Subtracting the difference from the minuend is equal to the minuend.

(4) pen addition and subtraction should pay attention to:

The same numbers should be aligned, and the single digits should be added and subtracted. When the numbers on the same digit add up to ten, they will go to the high place of 1. If the number in a number is not reduced enough, subtract 1 from the previous number and then add 10.

Three, quadrilateral:

Characteristics of (1) quadrilateral: It has four sides and four corners, and it is a closed figure.

(2) parallelogram features: the opposite sides are equal, the diagonal lines are equal, and it is easy to deform.

(3) perimeter:

Definition of perimeter: the length of a closed figure in one week.

The circumference of a rectangle = (length+width) ×2

Circumference of a square = side length ×4

Fourth, division with remainder:

Division with remainder: The remainder is always less than the divisor.

Five, multiple digits multiplied by one digit:

(1)0 times any number is 0, and 0 times any number equals any number.

(2) The multiplication rule of multiple digits multiplied by one digit is: each digit of multiple digits is multiplied by one digit in turn from one digit. If the product of a digit is ten, the first digit is entered as 1.