2. Observe the number of decimal places by using the changing law of product.

3. Application of the law.

A number (except 0) is multiplied by a number greater than 1, and the product is greater than the original number.

A number (except 0) is multiplied by a number less than 1, and the product is less than the original number.

When a number (except 0) is divided by a number greater than 1, the quotient is less than the original number.

When a number (except 0) is divided by a number less than 1, the quotient is greater than the original number.

4. Use letters to represent numbers. (Note: Numbers are multiplied by letters, and the multiplication sign is omitted)

5. Circulate decimal (error-prone, accurate to 1% = keep two decimal places)

6 units conversion (1 hectare = 10000 square meters, the ratio between time units is 60. 45 points =0.75)

7. Triangle area formula (finding the bottom).

8. The application of rectangular perimeter and area. (Formula and unit)

Given the perimeter and length, first find the width of 36÷2- 10=8 (cm).

Then find the area, 10×8=80 (square centimeter). According to the increased length 10+6= 16 (cm), the width is 80÷ 16=5 (cm).

9. The relationship between rectangle and triangle

10. Possibility

1 1. The relationship between parallelogram and trapezoid.

2. 1. The knowledge points are the same as those in Fill in the blanks 2. Put it another way.

2. Circular decimals are infinite decimals.

3. Decimal multiplication by integer has the same meaning as integer multiplication.

Decimal multiplication and integer multiplication have different meanings.

A triangle is half the area of a parallelogram with equal base and height.

Triangles with the same shape and size can be combined into a parallelogram.

Equal areas are not necessarily the same shape.

3. 1. Use letters to represent numbers.

2. Use number pairs to determine the position.

3. Fill in the blanks. Two knowledge points can be used.

Note that both option A and option D are greater than a, so you can compare them with examples. For example, a = 1, option a is 1.02, and d is 1÷0.02=50.

4. Examine the understanding of the decimal meaning

5. The relationship among dividend, divisor, quotient and remainder can be used. Quotient × divisor+remainder = divisor.

Four. 1. Note: 0. 1.0 1+8.5.

0. 1÷0.0 1 was mistaken for 1 ÷ 0.5438+0 in calculation.

2. The column vertical calculation of three questions needs to be "accurate to ten places", that is, one decimal place is reserved.

3. Apply the changing law of product and the law of multiplication and distribution. 17.6×84+ 176× 1.6

17.6×84 can be converted into 176×8.4.

Or convert 176× 1.6 into 17.6× 16.

4. The problem of solving equations

Pay attention to problem-solving methods and skills.

The equation in the form of ax+b=c regards ax as a whole.

The equation in the form of a(x+b)=c takes the formula in brackets as a whole.

Five, drawing questions:

1. Tag data 2. Computational verification

Method 1:

Shadow area = trapezoid area-blank triangle area

Method 2: Shadow area = sum of two shadow triangles = triangle area with a base of 60cm and a height of 30cm.

Six, 1. Check the problem of planting trees

Pay attention to keywords: planting at both ends, on both sides of the corridor

2. Investigate the quantitative relationship and solve the problem with equations.

Equivalence relation:

Planting trees in the third grade ×2- 16= planting trees in the fifth grade.

3. Encountered problems and sequence equations

Equivalence relation:

Speed of A × Time+Speed of B× Time = Total Distance

4. Investigate the application of polygon area.

The total area is obtained by the trapezoidal area formula.

Note: Paint consumption per square meter × total area = * * * required paint consumption.

5. Segmentation billing problem

Note: the shortage of 1km is calculated as 1km.

So 8.2 km is calculated as 9 km, which means 8.2 km ≈9 km.