(A) the basic concept of ratio.
1 and the division of two numbers are also called the ratio of two numbers. The quotient obtained by dividing the former term by the latter term is called the ratio.
2. Ratios are usually expressed by fractions, decimals and integers.
3. The last item of the ratio cannot be 0.
4. Compared with division, the former term of ratio is equivalent to dividend, the latter term is equivalent to divisor, and the ratio is equivalent to quotient.
5. According to the relationship between fraction and division, the former term of ratio is equivalent to numerator, the latter term is equivalent to denominator, and the ratio is equivalent to the value of fraction.
6. The basic nature of the ratio: the first term and the second term of the ratio are multiplied or divided by the same number at the same time (except 0), and the ratio remains unchanged.
(2) Find the ratio.
Find the ratio: divide the former term of the ratio by the latter term of the ratio.
(3) Simplify the proportion.
Simplify the ratio: divide the former term of the ratio by the latter term of the ratio to find the ratio of the fraction, and then change the ratio of the fraction into the ratio.
(4) Application of ratio.
The first application of 1, ratio: Given the sum of two or more quantities and the ratio of these two or more quantities, what are these two or these two quantities?
For example, there are 60 students in the sixth grade, and the ratio of male to female is 5: 7. How many boys and girls are there?
Topic analysis: 60 people are the sum of the number of boys and girls.
Solution: Step one, get each copy: 60÷(5+7)=5 people.
Step 2, find boys and girls: boys: 5×5=25, girls: 5×7=35.
2. The second application of the ratio: knowing the number of one, the ratio of two or more numbers, what are the other numbers?
For example, there are 25 boys in the sixth grade, and the ratio of boys to girls is 5: 7. How many girls are there? How many people are there in the class?
Topic analysis: 25 Boys is one of them.
Thinking of solving problems: Step 1, find each copy: 25÷5=5 people.
The second step is to find girls: girls: 5×7=35 people. Class: 25+35=60 people.