During this time, we learned a lot of knowledge. For example, discount, fractional multiplication and division, cuboid and cube surface area formulas are all our gains! Today we will talk about the key knowledge!

1, calculation method of multiplication of fractions and integers: molecules and integers are multiplied to make molecules, which can be simplified first.

2. Calculation method of fractional multiplication: numerator multiplies numerator, denominator multiplies denominator, and the fraction that can be reduced is reduced first.

3. Discount: 10% discount-current price = original price ×110.

4. Formula of cuboid surface area: S=2ab+2ah+2bh.

5. Cube surface area formula: S=a×a×6.

6. Definition of reciprocal in fractional division: the product of two numbers = 1, then these two numbers are reciprocal.

Next, I would like to share with you the "four-step" of solving fractional application problems taught by the teacher.

There are 6 children skipping rope, accounting for 2/9 of the total number of people participating in activities on the playground. How many people take part in the activities on the playground?

Step 1: The number of people skipping rope = the total number of people participating in the activity ×2/9.

Step 2: Substitute data 6=? ×2/9

Step 3: Formulating.

1. Division 6÷2/9 2. equation

Solution: suppose there are x people participating in the activity on the playground.

2/9x=6

Step 4: Calculate the result.

If the key sentence of the above question remains the same, it is known that the total number of people participating in the activity is 54, then how many people jump rope? Please answer with "four steps"! See what the difference will be.