Fractional equations are used to solve math in the 7th grade of junior high school

1. There are x people who donate for the first time.

4800/x=5000/(x+20)

x = 480 people who made the first donation.

2.Originally, it was stipulated that it would take x months to repair the road.

4+[1-4(1 x+1 (x+6)] (1 (x+6)=xx=12A: Originally, it was stipulated that it would take 12 months to repair the road.

3.The stationery factory used to process x sets of this stationery every day.

2500 x-1000 x-(2500-1000) x=100A: The stationery factory used to process 100 sets of this stationery every day.

4.Produce x products per day.

100/(x-10)+(220-100)/x=45.The original average speed of the passenger car is x kilometers per hour.

360/x-360/

x = 60 The original average speed of the passenger car is 60 km/h.

6.Beef in January this year was x yuan per catty.

20/x-20/

x = 10 beef in January this year 10 yuan per catty.

1. There are x people who donate for the first time.

then 4800 x = 5000 (x+20).

4800(x+20)=5000x

x=96000 (5000-4800)=96000 20=4800Do you have a mailbox?

1 The number of people who donate for the first time is x and the number of people who donate for the second time is Y.

The system of column equations is y-x=20

4800/x=5000/y x=480 y=500

3.Set the original one day to process x sets.

2500/x=1000/x+1500/（

Solution x=100

4.After setting up the improvement operation, X pieces of products are processed every day.

100/（x-10）+120/x=4

5.Let the original speed of the passenger car be x

360/x=360/（

The solution is x=60

6.Set the beef in January to get x yuan per catty.

The solution is x=10

5.Let the original speed of the passenger car be x

According to the title, 360 x=360 (

The solution is x=60

Check yourself to write.

1.There are x people.

4800/x=5000/x+2

x=482.The picture is.

3.Set the original one day to process x sets.

2500/x=1000/x+1500/（

Solution x=100

4.After setting up the improvement operation, X pieces of products are processed every day.

100/（x-10）+120/x=4

5.Let the original speed of the passenger car be x

360/x=360/（

The solution is x=60

6.Set the beef in January to get x yuan per catty.

The solution is x=10

Give points. As an important part of junior high school mathematics, fractional equations are used to test students' numeracy ability and problem-solving habits.

In the first step of the fractional equation to remove the denominator, you must pay attention to multiplying and dividing the same number on both sides, and you must not miss it.

The multiplication and division on the left side of the equation is x-4 multiplied by each term in parentheses.

Fractional equations must be rooted!! The results of root testing are divided into three types: root addition, no solution, and solution.

Breakthrough of major difficulties:

Example 2: What should we do if we encounter opposite numbers with denominator (x-2) and (2-x) as denominators?

Answer 2 is like **A2, you only need to multiply one of the denominators (x-2), in the step, note that (x-2) and (2-x) are approximated, leaving one -1, so x multiplied by (-1). Keep in mind that the opposite numbers are approximated, and there is only one (-1) left

If Xiaoli folds x + 1 paper crane per minute, then Xiao Jie folds x pcs.

x x+1=36 48 x=3 x+1=4 Answer: Xiaoli folds 4 pieces per minute, and Xiaojie 3 pieces.

Oops, the sophomore said that he hadn't done the application problem for a long time = = but he reacted for a long time in 5 seconds).

Let the sales of A be 5x and the sales of B be 3x in 03, and the sales of class B should be increased by y(1+20%) 5x (1+y) 3x=4 y= of 3 solutions

That is, an increase of 50%.

Suppose x should be added, and the sales of A in 03 are A, then the sales of B are 3A 5. From the meaning of the title, (1+:(1+x)*3a 5=4:3

18=12+12x

x = so category B sales should increase by 50 percent.

Simplify first, multiply left and right, and test.

1.There are x people who donate for the first time.

5000/(x+20)=4800/x

x=4802.Originally, it was stipulated that it would take X months to repair the road.

It is known that 4 months of construction of A = 6 months of construction of B.

So: 4 6=x (x+6).

x=123.Set the original daily processing x sets.

2500/x=1000/x+1500/

x=1004.After setting up improved operating methods, x products are produced per day.

100/(x-10)+(220-100)/x=45.The original average speed of the passenger car was x kilometers per hour.

360/(1+50%)x+2=360/x

x=606.Set the beef in January this year at x yuan per catty.

Catty. 20/x=5

Question 1 If there are x people in the first donation, then there are (x+20) people in the = donation, and the equation is 4800 x = 5000 (x+20) to get 4800 (x+20) = 5000x x solution x = 480 (people) Answer: There are 480 people in the first donation. Question 3 If the stationery factory originally processed x sets of this stationery every day, then it is now processed as a set every day, and the equation is 1000 x + 1500 to solve x = 100 (sets) Answer: The stationery factory originally processed 100 sets of this stationery every day.

Let the first time be x people, then the second time is 20+ people, 4800 divided by x = 5000 divided by 20x

Solution: Let A take x hours to complete alone, then B will take hours to complete alone, and the total amount of manuscripts will be set to 1 according to the title, so that A's speed is 1 x, and B's speed is 1 (1 x+4 5x)*4+6*4 5x=1 to obtain: x=12

It takes 12 hours to complete alone.

A: It takes 12 hours for A to complete alone.

Solution: It takes X hours for A to complete alone, then it takes 5x 4 hours for B to complete alone, then there is:

1/x+1/（5x/4））*4+1/（5x/4））*6=1

Solution: x=12