The calculation of the relationship between the three is relatively basic in the first grade of mathematics, but it is also very important. Usually, the calculation problems we come into contact with have the relationship between three numbers, and solving the relationship between these numbers requires us to master some basic knowledge and skills.
How to understand the relationship?
The relationship between them can be calculated by basic algorithms such as "addition, subtraction, multiplication and division". For example, if you know two numbers and need to ask for their sum or difference, you need to use "addition and subtraction"; If you know the ratio between two numbers and need to ask for another number, then you need to use "multiplication and division".
Let's look at a simple example: it is known that the age ratio of A and B is 2: 3, while the age ratio of B and C is 3: 4. What is the age ratio of A, B and C?
Because it is known that the age ratio of Party A and Party B is 2: 3, assuming that Party A is 2x and Party B is 3x, the age ratio of Party B and Party C is 3: 4, Party B is 3y and Party C is 4y. Because what we are looking for is the age ratio of Party A, Party B and Party C, we can use the method of "ratio times ratio" to get:
2x:3x:4y=6x:9x: 12y
Now we need to simplify the ratio and get the simplest ratio. Divide 9 and 6 by 3 and 12 and 6 by 4 to get:
6x:9x: 12y=2x:3x:4y
Because 2x:3x:4y is the simplest ratio, the age ratio of Party A, Party B and Party C is 2: 3: 4.
Solution to the problem of calculating the relationship between the three
As can be seen from the above example, it is not difficult to solve the problem of calculating the relationship between the three. As long as you master the basic problem-solving methods and skills, you can solve this kind of problem smoothly. Next, another example:
The relationship between hens, cocks and chickens in someone's home is that the number of hens is five, the number of cocks is twice that of chickens, and the number of chickens is three times that of hens and cocks. How many chickens are there in this family?
According to the relationship described in the topic, the following equation can be established:
Number of roosters = number of 2 chicks.
Number of chicks =3 (number of hens+number of cocks)
Substituting the first formula into the second formula, we get:
Chicken number =3 (hen number +2 chicken number)
Simplify the formula and get:
Number of chicks =3 hens +6 chicks
2 chickens =3 hens
5 chicks =5 hens+10 chicks.
5 chicks =5 hens+15 hens.
20 hens =5 chicks
Because the number of hens is known to be 5, the number of chickens is 20, and the number of cocks can be found by the number of cocks =2, which is 40.
Because the total number of chickens is the sum of the number of hens, cocks and chickens, there are 65 chickens in this family.
summary
As can be seen from the above examples, it is very important to master the basic knowledge and skills of calculating the relationship between the three, so as to flexibly use mathematical knowledge to calculate in daily life.
In the process of learning, we need to pay attention to appropriate exercises and deeply understand the problem-solving ideas of each topic, so as to further improve our mathematics level.