I. Length and area of the third unit

1, cognitive length unit

(1) Know centimeters and meters.

(2) Establish the concept of length unit.

2. Calculation of perimeter and area of rectangle and square

Calculation method of (1) perimeter.

(2) Calculation method of area.

(3) Distinguish the difference between perimeter and area.

Unit 4 Fractions and Decimals

1, the meaning and nature of the fraction

The meaning of (1) score: the relative relationship between part and whole.

(2) The nature of the score: general score, reduced score, greatest common divisor, least common multiple, etc.

2, the meaning of decimal and reading and writing methods

The meaning of (1) decimal: a numeric expression with the denominator of 10.

(2) Decimal reading and writing method: integer part, decimal point and decimal part.

(3) The nature of decimal: the integer part, decimal point, decimal part and denominator have the same nature.

3. Mutualization of Fractions and Decimals

Fractionation of (1) decimals.

(2) Decimal method.

Use of decimals

1. Measurement or calculation: measure or calculate common decimals, such as 0.5m, 0.2kg, 0.35s, etc.

2. Temperature: When temperature is expressed, the numerical value in degrees Celsius is expressed in decimals, for example, 25.5 degrees Celsius.

3. Price: When shopping, use decimals to express commodity prices, such as: 0.99 USD, 2.5 yuan RMB, etc.

4. Scientific counting method: In scientific research, some tiny numbers or larger numbers are expressed by decimals, such as 0.0000000016g, 1000000000 meters, etc.

Purpose of score

1. Performance evaluation: In the field of education, scores are widely used to evaluate students' academic performance. Students' test scores are usually expressed in percentage system, which is used to measure students' mastery and academic performance.

2. Sports competition: In sports competition, scores are used to record the progress and results of the competition. Used to reflect the winning or losing relationship of the game.

3. Bank loans: In the financial field, the interest rate of bank loans is often expressed in the form of fractions. Indicate how much loan amount needs to be paid as interest each year.

4. Dietary nutrition: In food packaging, nutrients are usually expressed in percentage. Indicates how much a substance accounts for the total weight of food.

5. Health assessment: Doctors often use scores to assess patients' health.