1, the ratio of two numbers indicates the division of two numbers, and the latter term of the ratio cannot be 0. Such as: 5: 7 = 5 ÷ 7

2. The components of comparison are: the previous paragraph, the comparison number and the last item.

3. Simplest integer ratio: the former and the latter are two integers that are prime numbers, and this ratio is called the simplest integer ratio.

4. Basic properties of ratio: The first term and the last term of ratio are multiplied or divided by the same number (except 0) at the same time, and the ratio remains unchanged, which is called the basic properties of ratio.

5. Relationship and difference between ratio, fraction and division. The relationship between ratio and division; The former paragraph is equivalent to dividend, the latter paragraph is equivalent to divisor, and the comparison symbol is equivalent to divisor. The ratio is equivalent to the quotient. The relationship between ratio and score; The former is equivalent to numerator, the latter is equivalent to denominator, and the comparison symbol is equivalent to fractional line. The ratio is equivalent to a fractional value. Such as: 2: 3 = 2 ÷ 3

6. The difference between simplifying ratio and seeking ratio. Simplified proportion: the former item and the latter item are multiplied or divided by the same number at the same time (except 0). (The former item, comparison symbol and the latter item must exist) Find the ratio: the former item ÷ the latter item = a number (which can be a fraction, decimal or integer).

Second, the application of ratio

1, given the total amount and the ratio of these two quantities, find the proportional distribution. If the ratio of these two numbers is A: B method 1: (1), first find the total number of copies, and A+B = the total number of copies (2) and then find the fraction of each quantity in the total number of copies.

Method 2: (1) A+B = total number of copies (2) total number of copies/total number of copies = each number of copies (3) a; Each share of a = the total amount of a; b； Each share of b = the total amount of b Example: Concrete is a mixture of cement, sand and stone in the ratio of 2: 3: 5. There are 50 tons of concrete at present. How many tons of cement, sand and stones are needed?

2. Know the ratio of these two quantities to one of them and find the other quantity.

Methods: Enlarge the former item and the latter item by the same multiple at the same time. If the ratio of these two numbers is A: B, the total amount of A .. (1) The total amount of A = multiple (2) The multiple of B = the total amount of B.

At present, chickens and rabbits are in the same cage, and the ratio of chickens to rabbits is 5:7. There are 65,438+005 chickens. How many rabbits are there in the cage?

3. Know the ratio of these two quantities and one of them, and sum them up. Method: If the ratio of these two numbers is A: B, then the total amount of A .. (1) The total amount of A = multiple (2) The multiple of B = the total amount of B.

4. Knowing the ratio and difference of these two quantities, the method of finding the total amount is: (1) A-B = number of copies (2) difference ÷ number of copies = number of copies (3) number of copies (A+B) = total amount (3) total amount of a+total amount of b = total amount.

At present, chickens and rabbits live in the same cage, and the ratio of chickens to rabbits is 5:7. There are 105 chickens. How many animals are there in the cage?

At present, chickens and rabbits are kept in the same cage. The ratio of chickens to rabbits is 5:7, and there are 28 fewer chickens than rabbits. How many animals are there in the cage?