X stands for what is sought. What is three times three?

2. Fraction multiplied by integer, denominator unchanged, the product of numerator multiplied by integer is a numerator.

Fraction multiplied by fraction, numerator multiplied by numerator, denominator multiplied by denominator can be subtracted first.

3, a number multiplied by a true fraction, the product must be less than the original number;

Multiply a number by a number equal to 1, and the product is equal to the original number;

Multiply a number by a false fraction greater than 1, and the product must be greater than the original number.

4. A cuboid has six faces, each of which is generally rectangular (in special cases, two opposite faces are square), and the areas of the opposite faces are equal. There are 12 edges, and 12 edges can be divided into three groups: four in length, four in width and four in height, and the length, width and height are equal respectively. There are eight vertices, and each vertex consists of three sides, one side represents the length, one side represents the width and one side represents the height.

A cube has six faces, and each face is an equal square. There are 12 sides, and the length of 12 sides is equal, which is called the side length of a cube. There are eight vertices. Cubes are special cuboids.

6. The side length of a cuboid = (length+width+height) ×4

Side length of cube = side length × 12

7. The sum of the areas of six faces of a cuboid is called the surface area of a cuboid.

Area of cuboid = length × width

The surface area of a cuboid = length× width× 2+length× height× 2+width× height× 2, which is expressed by letters as: S=2ab+2ah+2bh.

8. The sum of the areas of the six faces of a cube is called the surface area of the cube.

Area of each face of the cube = side length × side length

The surface area of a cube = side length × side length ×6, expressed in letters as: S=6a2.

9. Exposed area = the area of one face × the number of exposed faces.

10. If the product of two numbers is 1, then these two numbers are called reciprocal, and one number is called reciprocal of the other. The reciprocal of 1 is 1. 0 has no reciprocal.

1 1, the law of fractional division: dividing by a number (except zero) is equal to multiplying the reciprocal of this number.

12, when divisor

When divisor = 1, quotient equals dividend;

When divisor >; 1, the quotient is less than the dividend.

13, the size of the space occupied by an object is called the volume of the object. Commonly used unit of volume has cubic meters, cubic decimeters and cubic centimeters.

The volume of the object that a container can hold is called the volume of the container. The commonly used unit of volume are liters and milliliters.

Unit of volume is used to calculate the volume of objects, and unit of volume is generally used to calculate the volume of liquids and gases.

14, 1 m3 = 1000 cubic decimeter 1 cubic decimeter = 1000 cubic centimeter.

1 cubic decimeter = 1 liter

1L = 1000ml 1 cm3 = 1ml

15, cuboid volume = length× width× height V=abh.

Volume of cube = side length × side length × side length V=a?

Volume of cuboid (or cube) = bottom area × height V=Sh

16. When measuring the volume of an irregular object, you can put the irregular object into a container filled with water, and the volume of rising water or overflowing water is the volume of this object.

17, the order of decimal mixing operation is the same as that of integer mixing operation, which is to calculate multiplication and division first, and then add and subtract. If there are brackets, count the inside of brackets first, and then count the outside of brackets.

The arithmetic of integers also applies to decimal arithmetic.

18, find the fraction (or percentage) of a number and calculate it by multiplication;

Know what the score of a number is, find this number and calculate it by division.

19, the number indicating that one number is the percentage of another number is called percentage. Percentage is also called percentage, percentage.

20. Pass rate = number of people who passed ÷ total number of people.

Survival rate = number of trees survived/total number of trees planted.

Flour yield = flour weight/wheat weight.

Qualified rate = number of qualified products ÷ total number of products.

Attendance = Attendance ÷ Total number of people

Hit ratio = number of hits ÷ total times

Excellent rate = excellent number ÷ total number.

Germination rate = number of germinated seeds/total number of seeds.

2 1, decimal as a percentage: first move the decimal point to the right by two places, and then add% after it.

Fractions are converted into percentages: first, the fractions are converted into decimals (three decimal places are reserved when they are not used up), and then the decimals are converted into percentages.

Decimal percentage: remove% first, and then move the decimal point to the left by two places.

Percentage component number: first, the percentage component is a score of 100, and then it is simplified; Or convert the percentage into decimal and then into component number.

22, bar chart can clearly see the number of each item, easy to compare.

You can clearly see the percentage of each part in the total in the fan-shaped statistical chart.

The statistical chart of dotted line can clearly see the change of quantity.

23. The number that appears most frequently in a set of data is called the mode of this set of data.

Arrange a set of data from small to large (or from large to small), and the middle number is called the median of this set of data. When the number of a set of data is even, the median takes the average of the middle two numbers.

Average value = total quantity/total number of copies

Review of key knowledge

1, unit conversion law: large units are converted into small units, multiplication rate; Divide small units into large units according to the forward speed.

2. Common length units: kilometers, meters, decimeters, centimeters and millimeters.

1 km = 1 000m1m = 10 decimeter.

1 decimeter = 1 0cm1cm =10mm

3. Public area units: square kilometers, hectares, square meters, square decimeters, square centimeters and square millimeters.

1 km2 = 1 00ha1hectare =10000m2

1 km2 = 1000000 m2

1 m2 = 100 square decimeter 1 square decimeter = 100 square centimeter

1 cm2 = 100 mm2

4. Common mass units: tons, kilograms and grams.

1 ton = 1 000kg1kg =1000g

5. Common time units: year, month, day, hour, minute and second.

1 year =365 days (366 days in leap year) 1 year = 12 months.

1 day =24 hours 1 hour =60 minutes 1 minute =60 seconds.

6. The plane figures we have studied are rectangles, squares, parallelograms, triangles, trapeziums and circles, and the three-dimensional figures we have studied are cuboids and cubes.

7. The perimeter of a rectangle = (length+width) ×2 The perimeter of a square = side length ×4.

Length of rectangle = perimeter ÷2- width of rectangle = perimeter ÷2- length

Side length of a square = perimeter ÷4

8. Rectangular area = length x width squared = side length x side length

Area of parallelogram = bottom area x height triangle = bottom x height ÷2

Trapezoidal area = (upper bottom+lower bottom) × height ÷2

9. Length of rectangle = width of region = width of rectangle = length of region.

The base of parallelogram = the height of parallelogram = the base of parallelogram.

Base of triangle = area ×2÷ height = area ×2÷ base of triangle.

Trapezoidal height = area ×2 (upper bottom+lower bottom)

The sum of the upper and lower bottoms of the trapezoid = area ×2÷ height.

Upper bottom surface of trapezoid = area ×2÷ height-lower bottom surface

Trapezoidal bottom = area ×2÷ height-upper bottom

10, the addition and subtraction of fractions with the same denominator, the denominator remains the same, only the numerator is added and subtracted, and the result is probably the simplest fraction.

The addition and subtraction of fractions with different denominators are divided into fractions with the same mother number first, and then added and subtracted.

1 1, the relationship between fraction and division: dividend/divisor =

12, the basic nature of the fraction: both the numerator and denominator of the fraction are multiplied or divided by the same number (except 0), and the size of the fraction remains unchanged.