Junior 3 Mathematics Equation Application Please answer in detail, thank you 22 10 24 51

Now that it is planned to reinforce the embankment x meters per day, it was planned that it would take time 2240 (x-20) to reinforce x-20 per day

The current plan takes 2240 x

The planned completion time is 2 days shorter than the original plan, which is: 2240 x - 2 = 2240 (x-20).

If the original plan is to strengthen the embankment x meters per day, then the equation can be listed according to the meaning of the problem.

2240/x-2240/(x+20)=2

x = 140 meters.

x+20=160 meters.

It used to be 140 meters per day, but now it is 160 meters per day.

Solution: Now it is planned to strengthen the embankment x meters per day, and it was originally planned to strengthen x - 20 meters per day.

2240/（x-20)-2240/x=2

If the original plan is to strengthen the embankment x meters per day, the equation can be listed according to the meaning of the problem.

2240/x-2240/(x+20)=2

x=140x+20=160

A: It used to be 140 meters per day, but now it is 160 meters per day.

2240 (x-20)} 2240 x=2 because the length of the reinforcement planned to be increased by 20 meters per day compared to the original plan.

So it was originally planned to strengthen the length of (x-20) per day

Therefore, the number of days required for reinforcement was originally planned to be 2240 (x-20), and now the number of days required for reinforcement per day is planned to be 2240 x

In addition, the number of days required to complete the embankment reinforcement work was shortened by 2 days compared to the original plan.

So {2240 (x-20)} 2240 x=2

[1]∵（n-2）（2n+3）=0

n-2)=0 or (2n+3)=0

n=2 or n=

2] (2x-1) square = 9

2x-1)=±3

x=2 or x=-1

3] (2x-1)(x+1)=(3x+1)(x+1) (x+1)=0 or (2x-1)=(3x+1)x=-1 or x=-2 (both have two solutions, pay attention to the situation-by-case discussion).

（1)（n-2）（2n+3）=0

There are two solutions n-2=0 or 2n+3=0

Get n1 = 2 n2 = -3 2

2）（2x-1）²=9

Then 2x-1=3 2x-1=-3

x1=2 x2=-1

3)(2x-1)(x+1)=(3x+1)(x+1) The above formula is simplified 2x-1=3x+1 or x+1=0x1=-2 x2=-1

1.Enterprise processing a large machinery and equipment lubricating oil 90kg, the reuse rate of oil is 60%, according to this calculation, the actual oil consumption of processing a large machinery and equipment is 36kg, the actual consumption is: the total amount of oil - reusable oil = 90-90 * 60% = 3kg so in the first workshop through technological innovation, the actual fuel consumption of processing a large machinery and equipment will be 70kg, the weight utilization rate of oil is still 60, his actual fuel consumption: 70-70* 60%=28kg

2. This is a little more complicated, the amount of oil used is reduced by x kg, so the amount of oil used is 90-x kg.

Then, according to the "lubrication oil consumption decreases by 1 kg, the reuse rate of the oil consumption will increase, and the reuse rate of the oil will be (60+, so there is.

90-x)*[1-(60+

x-90)*(x-25)=750

x 2-115x+1500=0, we get x=100 or x=15, obviously x=15, so, the amount of oil used is 75 kg, and the reuse rate of oil is 84%.

1 Solution: Let this incoming plane fly the farthest.

The source x kilometers should be returned, the column.

Bai Cheng. x/600+x/550=

600+550）x=

x=1320

Answer: This DU aircraft flew up to 1320 kilometers and should return to 2 solutions: set up two factories A and B in January to actually produce x, y lathes, the equation x + y = 422

x Do the math for yourself.

3 Solution: Let Xiao Wang's speed be x meters per second, then Uncle's speed will be 400 meters per second (x+

x=5, then Xiao Wang's speed is 5 meters per second, then Uncle's speed is meters per second, and the time is t

t = 160 seconds.

4 Solve the thickness of this plastic wrap is x mm.

pai*d*d-pai*d*d）/4=60xx=

The thickness of this plastic wrap is set to millimeters.

1.If you fly in x hours, you will fly back for hours.

Since the interval that flies in is equal to the interval that flies back.

So we get 600*x=(

Solution: 600*x=2530-550*x

1150*x=2530

x = the plane flew in 600 * kilometers and returned.

2.Solution: Factory A originally planned to produce x sets of lathes, and factory B originally planned to produce Y sets of lathes, according to the topic.

x+y=360 (1)

112%*x+110%*y=400 (2) The solution yields x=200 (sets).

y=160 (sets).

Therefore, factory A over-production lathe: 200 * (112%-100%) = 24 (sets) Factory B over-production lathe: 160 * 10% = 16 (sets) [Note: one percent is 10%].

3.Let Xiao Wang run x meters per second, then Uncle will run meters per second, and get 400 (x+) according to the title

x=5 Xiao Wang runs 5 meters per second, and Uncle runs 5 meters per second.

400 (seconds).

The next day, Xiao Wang planned to run in the same direction with his uncle, and his uncle met him again every 160 seconds4The average diameter is.

The length of the plastic wrap is 60m=6000cm, so there are a total of 6000 ( layers, then the thickness is.

Solution: If you make x tabletops, you need to make 4x table legs.

The table top needs wood x 50 cubic meters, and the table legs need wood 4x 300 = x 75 cubic meters.

So there is x 50 + x 75 = 5

3x+2x=750

5x=750

x=150 shows that 150 tables were made, and 150 50=3 cubic meters were used to make tabletops.

If x cubic meters are used as table legs, the table top is 5-x cubic meters.

300x/4=50*(5-x)

x=2 so 2 cubic meters for table legs and 3 cubic meters for tabletops.

3 sides for the table top, 2 sides for the legs.

50x=(5-x)*300/4

As can be seen from the title, a table top costs 1 50 cubic meters of wood, and a table leg costs 1 300 cubic meters of wood.

The ratio of the number of legs to the table top should be 4:1

So let's make the following equation: let the number of tables be x and the number of legs be y:

has 4x=y(1);

x/50+y/300=5(2);

Solving this equation gives us x=150; y=600 means that the best method is 3 cubic meters for the table top and 2 square meters for the table legs.

Because. 3\2s+t=8\3s-2t=3

So. 3 2s+t=8 3s-2t=1 The denominator is the same as that of the stool 3 early.

For 24 so.

24 Tongque 8 (2s + t) = 24 3 (3s-2t) = 24 72 Divide the denominator.

8(2s+t)=3(3s-2t)=72

Simplification of thick limbs. 16s+8t=9s-6t=72

16s+8t=72

9s-6t=72②