We know that an object, a unit of measurement or a whole composed of many objects can be represented by the natural number "1", which we usually call the unit "1". For example, the "three good" students in Class One of Grade Five account for the whole class, which should be understood as: regard the class size as a unit of "1" and divide it into 9 parts on average. 2 copies of Miyoshi students; Another example: the surface of the earth is covered by the ocean. It should be understood here that the surface area of the earth is "1", which is divided into 100 parts on average, and the area covered by the ocean is about 7 1 part.

How can we correctly calculate the number of units "1"? In the teaching process, teachers should pay attention to guiding students to read and examine questions carefully. Pay special attention to the correct understanding of key words, words and sentences; Students should be guided to understand the relationship between quantity and quantity.

In the teaching process, we often encounter the following problems:

One, find the fraction that one quantity is another quantity.

Example: 8 red flowers and 65,438+02 white flowers. What is the number of red flowers?

Tip: The number of "1" is the number of white flowers.

Understanding: Divide the number of white flowers into 12, and the number of red flowers is 8.

Formula: 8÷ 12=8/ 12, that is, the number of red flowers is 8/ 12 of that of white flowers.

Second, what is a given score? Find this quantity.

N: The number of red flowers is 8, which is 4/5 of the number of white flowers. Find the number of white flowers.

Tip: Quantity of unit "1": quantity of white flowers.

Understanding: Divide the number of white flowers into five equally. There are four such red flowers.

Solution 1: 8÷4=2 (flower)

2×5= 10 (flower)

Solution 2: 8÷4/5= 10 (flower)

Option 3: Let there be X white flowers.

4/5x=8

x=8÷ 4/2

x= 10

The number of white flowers is 10.

Third, what is the score of a quantity?

Example: The number of white flowers is 10, and the number of red flowers is white. How about the number of red flowers?

Tip: Quantity of unit "1": quantity of white flowers.

Understanding: Divide the number of white flowers into five and the number of red flowers into four.

Solution 1: 10÷5=2 (flowers)

2×4=8 (flower)

Solution 2: 10×4/5=8 (flower)

That is, there are eight white flowers.

Finding out the number of units "1" is the key to solve the problem. If students can correctly find out the quantity "1", it means that students have this kind of learning ability, and educating students is to teach them a kind of ability. Ability to analyze and answer questions independently.