The fractional equation of the second year of junior high school mathematics is a master to help

1.Set: The ship sails x kilometers per hour against the water, and y kilometers per hour when sailing along the water.

120/x=120/y +2

12/y=8/x

Solve the system of equations, x=20, y=30

A: The ship sails against the current for 20 kilometers per hour.

2.Setting: X students from Class A participated in this disaster relief activity.

200/x +1=400/(30+x)

Solve the equation where x1 = 120 (rounded) and x2 = 50

A: How many students from Class A participated in this disaster relief activity?

3.Set: It takes x days to complete this work with the new technology.

52(x+6)=40x*

Solve the equation to get x=39

A: The number of days it takes to complete this work with the new technology is 39 days.

120/(x+y) -120/(x-y) =212/(x+y)=8/(x-y)

find x-y

2: (200+200) (30+x) = (200 x) +13: initial productivity per 1:

n 52new productivity per 1 : n 52 * = 3n 104n ( 3n 104 )*40 ) n 52 = 6find n

Downstream velocity = velocity of the boat in still water + velocity of the current.

Velocity against the water = velocity of the boat in still water – velocity of the current.

Let the hydrostatic velocity be x, then the downstream velocity is x+2 and the reverse velocity x 280 (x+2)=80 (x 2) 1

x=18km/h

Solution: Set the speed of the ship in still water to be x kilometers per hour.

From the meaning of the question, we get 60 (x+2)=48 (x-2) and solve it x=18

After examination, x=18 is the root of the original equation.

A: The speed of the boat in still water is 18 km/h.

Let the ship have a velocity of x in still water

then 80 (x+2)+1=80 (x 2).

So the square of x = 324

i.e. x = 18

15 x is the time for the cyclist 15 3x is the time for the car Since the bicycle is half an hour away, the equation 15 x = 15 3x+ can be listed

x=20 is the root of the original equation after testing, and I hope it can help you.

Fractional equation exam questions?

If Mr. Zhang's walking speed is x kilometers per hour, then the speed of cycling is 3 x kilometers [(3+3+.]

Solution: x=5 kilometers is the speed per hour of walking.

Bicycle speed per hour = 5 * 3 = 15 km/h.

Solution: If Mr. Zhang's walking speed is x kilometers per hour, then his cycling speed is 3 kilometers per hour.

20 minutes 1 to 3 hours.

Solution: x 2.........The speed of walking 3x 3 2 6 km ......... hThe speed of the ride.

Let's take Mr. Zhang's walking speed to x kilometers per hour, i.e. to ride a bicycle at a speed of 1 3 hours per minute.

That is, Mr. Zhang's daily walking time to work, and the time to use a bicycle to pick up Xiao Ming is (3+3+.

The following equation is obtained:

Here's how it works: multiply both sides by 3x:

x=6 means that Mr. Zhang's walking speed is 6 km-h, and the speed of cycling is 18 km-h.

Two solutions: if the walking speed is xkm h, then the bicycle speed is 3x km h20 minutes = 1 3h

1 kind; The school is located between Xiao Ming's house and Mr. Zhang's house.

The equation is (3+

x=4 Therefore, the walking speed is 4km h, and the bicycle speed is 12km h2 types: the school is not between Mr. Zhang's house and Xiao Ming's house.

Equation (3+

x=5 Thus, the walking speed is 5 km h and the bicycle speed is 15 km h

Solution: If Mr. Zhang's walking speed is x kilometers per hour, then Mr. Zhang's cycling speed is 3x kilometers per hour.

From the meaning of the question, (3+3+ -= 1 3 solution x= 5 3x=15

A: Mr. Zhang walks at a speed of 5 kilometers and cycles at a speed of 15 kilometers.

Set the walking speed to x and the cycling speed to 3x.

The teacher went to pick up Xiao Ming and then went to school, and the total distance was kilometers. Column:

Multiply both sides of the equation by x-3, and this is a one-dimensional equation.

It should be noted that after the solution is obtained, it must be substituted into the original equation, and if the denominator is 0, it is the root increase.

1) Set a per hour to handle x + 30, b to handle x per hour, 900 x + 30 600 x

a：60b：90

If it takes x days to complete the task after adopting the new technology, it will take x+6 days for the original technology to complete the task.

The productivity per person per day with the original technology is: 1 52 (x+6).

The productivity per person per day with the new technology is: 1 40x

From the problem: 1 52 (x + 6) * (1 + 50%) = 1 40x solution: x = 39

Inspection:. With the ambush line...

With the introduction of the new technology, it will take 39 days to complete this task.

Let the original amount of work completed per person per day be x, and the original time is y days, and the potato trouble is derived from the title.

52xy=40(1+50％)x(y-6)

52y=60y-360

8y=360y=45

That is, the number of days required to complete this task with the new technology is 39 days.

1, a total of 20 hectares, originally m (a 20) t per hectare, now (ma+20a) 20t

2, (1) Let the speed of the second group be x meters and seconds.

x=1/12

2) Let the speed of the second group be x meters and seconds.

60t+h/(ax)=h/x

x=(a-1)h/(60at)

1,1/x-1=2x

2,x2-a2

4,5 + root number 14,5 - root number 14

5,59,a

Solution: Let A make x parts per hour, then B makes (35 x) parts per hour.

90/x＝120/（35－x）

3/x＝4/（35－x）

4x＝105－3x

7x＝105

x＝15………A makes 35 15 20 parts per hour .........The number of parts made per hour.

Solution: Let A make x parts per hour, then B makes (35-x) parts per hour, 90 x = 120 (35-x).

The solution is: x=15, 35-x=20, and empirically: x=15 is the root of the equation.

A: A does 15 pieces per hour, then B does 20 pieces per hour.

Let A do x per hour and B make y per hour.

90/x=120/y

x+y=35

Solution, get x=15, y=20

Suppose A does x per hour and B does y per hour.

by the title. 90/x=120/y

x+y=35;

The solution is x=15;y=20；

In other words, A made 15 and B made 20.

Let the number of things A does per hour be x, and the number of things B does per hour is y.

So: 90 x = 120 y, x + y = 35

At last...