Estimation refers to the calculation or evaluation of numerical results by approximate method. In the third grade mathematics, estimation is one of the key points in learning. Here are some methods and skills about the third grade estimation questions.

First, the basic method of estimation:

Approximate rounding of numerical values.

Use known numerical relationships for estimation.

Turn the problem into a simpler form for estimation.

Second, the estimation technology and examples:

Hint 1: Approximate rounding

Approximate rounding method is used to estimate the value, which avoids complicated calculation.

Example 1:

You bought apples in the supermarket. The price of each apple is 3.5 yuan. You bought 12 apples. What is the total price?

Solution: approximate the 3.5 yuan price of each apple to 4 yuan, and then calculate the total price of 12 apples, that is, 4 yuan/× 12 apples =48 yuan.

Tip 2: Use numerical relationships.

Using the known numerical relationship to estimate, the problem is simplified.

Example 2:

Xiaoming's home is 600 meters away from school. His walking speed is 80 meters per minute. How long does it take him to go to school on foot?

Solution: Transform the problem into solving the value of 600 divided by 80, and approximately calculate 600÷80≈7.5.

Therefore, it takes about 7.5 minutes for Xiao Ming to walk to school.

Tip 3: Simplify the problem.

Simplify complex problems into simple ones for evaluation.

Example 3:

Xiaoli made a multiplication card, which read 12× 17=? She estimated to ask, and the result?

Solution: approximate 12 to 10, 17 to 20, and then calculate 10×20=200.

So the estimated result is 12× 17≈200.

Third, summary:

In the third grade mathematics, estimation is an effective method to help students calculate and solve problems quickly. By approximate rounding, using numerical relations, simplifying the problem can help students estimate more flexibly and accurately.

Knowledge expansion

To calculate math problems quickly, there are some skills and methods that can help you improve the calculation speed. Here are some suggestions:

Use approximation: If the number in the question is large, you can use approximation to calculate. For example, take a number to the nearest integer or a decimal to the nearest fraction. This can simplify the calculation, and the result is usually within the acceptable range.

Apply mathematical operation rules: understand and apply mathematical operation rules (such as multiplication and division, factorization, etc.). ) can help you simplify the calculation process. Turning the problem into a simpler form usually speeds up the calculation.

Use mental arithmetic skills: mastering some mental arithmetic skills can improve the calculation speed. For example, learn multiplication table, quickly calculate square number, rounding and other skills.

Using mathematical formulas and special properties: For some common mathematical problems, mastering the corresponding formulas and special properties can directly give the results without detailed calculation. For example, using the identity of trigonometric function to solve trigonometric function problems, or using the special properties of square root to calculate roots.

In short, strengthening the study and practice of mathematical knowledge and skills can improve the calculation speed and solve mathematical problems more efficiently.