I can t figure it out, elementary school math? Help.

This kind of problem should be a graph of equations.

1) Let the first meeting time of A and C take x minutes, and the speed of B is ym minutes.

then there is 40x+xy+210=490 (1).

Because the ratio of C to and fro is 140:100=7:5

So CB: D'c = 7:5, i.e. cb = (7 12) xy

Then there is 280x+2*(7 12)xy=490*2 (2) simultaneous equations (1) and (2) to obtain: y=60

At this time, the distance between A and C is: 210-(40+60)*

At this time, the distance between A and B: 140-(40+60)*

So B walks 60m per minute, and the next time A and C meet, A and B are 90m apart.

I really don't understand why you guys are doing it wrong.

The list of equations should be:

Let the first encounter time be t1 (C and B), the second encounter time be t2 (A and C) B velocity is y, and the total time is x, that is, x=t1+t2

1,(240+y)t1=490

2,240t1-40t1=(40+240)t23,t1+t2=x

4,40x+xy=490-210

Simultaneous solution, Y can be calculated

Let it take 1 second for C to reach B for the first time, and it takes t2 seconds for C to travel from B to A, and B's velocity is x

1. 490-240t1=xt1

2. 490-40t1-xt1=240t2+40t23.490-40t1-xt1-40t2-xt2=210 synthesis.

80-4 76 capsules.

3800 95% 4000pcs.

A: The germination rate of seeds is 95%, and it takes 4,000 soybeans to live 3,800 soybean seedlings.

（80-4）÷80＝

A: The germination rate is 95%.

Germination rate of germinated seeds Total number of seeds.

3800 95% 4000 trees.

A: 4,000 trees are needed.

1、（80-4）÷80=76÷80=

The germination rate of the seeds is 95%.

95% = 4000 capsules.

4,000 soybean seeds need to be sown.

Out of 80 seeds, four of them did not germinate, and the germination rate is (80-4) 80, if you need 3,800 seeds, divide by 3,000.

（80-4）÷80=95%

The germination rate of the seeds is (95), and if 3800 soybean seedlings are needed, 4000 soybean seeds need to be sown.

Germination rate Number of germinations Total 76 80 95%.

If you need 3800 seedlings, you need to sow 3800 95% 4000. So you need to sow 4,000 seeds.

Germination rate = (number of seeds - number of seeds that did not germinate) Number of seeds, so germination rate in this question = (80-4) 80=

The number of seeds that need to be sown = the number of trees that need germination rate.

So the number of trees that need to be planted = 3800

(1) Seed germination rate = (80-4) 80 = 76 80 = 95% (2) Equation:

Solution: Suppose x soybean seeds are needed.

95%x=3800

x=40002).

4000 (grains).

Germination rate of seeds:

Number of soybean seeds to be sown:

The germination rate of the seeds is 76 80 = 95%.

Seed 3800 is required

Germination rate = (80-4) 80=

Sowing required: 3800 95%=4000 (grains).

1.Germination rate:

First, calculate how many 80 seeds germinated, 80-4 = 76 and then germination rate = number of germinations divided by the number of seeds sown, i.e. 76 80 = 2Find the number of soybeans sown. To germinate 3800 seeds, that is, now know the germination rate, know the total number to germinate, and find the number of seeds.

That is, 3800, to sow 4000 seeds.

Number of germinated seeds: 80 4 76 (seeds).

Germination rate: 76 80 95

3800 95 4000 (granules).

A: The germination rate of the seeds is 95, and 4000 soybean seeds need to be sown.

1, v A 1 40, A does 20 days, the rest is 1 2Since v A B 1 36 so, 1 2 divided by 1 36 equals 18 days.

2, v A 1 9, v B 1 8, A open 5 minutes, then 1-5 9 4 9 B still need time: 4 9 divided by 1 8 equals 32 9 minutes 3, the amount of work is 1, the speed difference between A and B is 1 80, and A 10, B can be completed in 4 days.

So, 10 days for A and 10 days for B + 10 80, that is, B completes 1-1 8 7 8 in 14 days

So, v B 7 8 divided by 14 equals 1 16, v A 1 16 + 1 80 3 40

Therefore, it takes 40 3 days for A to complete and 16 days for B.

4, 10 people for 12 days, that is, v 1 120 per person per day, 18 people for 3 days, that is, 1 120 times 18*3 9 20

To complete 3 4, i.e. 3 4-9 20 3 10 is not completed.

So: 3 10 divided by 4 120 equals 9 people. That is, 9 people work in 4 days.

9 First question"Now do it alone for 20 days"It is not specified who will do it first, the second: if the storage capacity of the pool is 1, then the irrigation rate of A is 1 9, and the irrigation rate of B is 1 8

So according to the title: it takes x minutes to fill up.

5*（1/9）+x*（1/8）=1

Solution x=32 9

That is, it takes 32-9 minutes to fill up.

Question 3: Let this project be 1, B completes x every day, then A completes (x+1 80) every day, according to the question: 4*(x+x+1 80)+6*(x+1 80)=1 solves x=1 16

Therefore, A completes 1 16 + 1 80 per day, and B completes 1 16 per day, that is, A completes it alone, and it takes 40 3 days; It takes 16 days to complete it individually.

Question 3: If the quantity of work is 1, then the amount of work completed per person per day is 1 (10*12) according to the question: set a total of x people for 4 days.

18*3*[1/（10*12）]+x*4*[1/（10*12）]=3/4

The solution is x=9, so there are 9 people in 4 days.

After reading so much, I believe that the landlord has figured out the first question and will already do it.,Do it yourself and see if you don't understand it.,It's asking.。

This is a question from the first year of junior high school, and it is a question from elementary school.

Two-ninths by three-eighths plus three-eighths plus sevenths by ninths.

Two-ninths + seven-ninths) multiplied by (three-eighths three-eighths) multiplied by 1 times sixths of eighths.

Two hundred and twenty-five out of eight.

If it's not the simple operation required, it's not simple, but it's more troublesome.

a+b=240 ①

c+b=224 ②

c+d=212 ③

a+d=213 ④

This question is a contradiction and there is no solution.

Because the equation - gives a-c=16

Equation - gives c-a=1

a c is unsolvable.

<> look at the Duan Xiaozhou burning dates.

<> the map of the bridge to tell the clear bridge.

<> Xi looked forward to the free opening of the belt to help Dou Lu.

The factory produces one kind of part, every 6 pcs in a box, now repacked, 7 boxes of 56 pcs, how many are in each box now? How many more boxes are there now?

Now there are 56 7 = 8 per box.

Now there are 8-6 = 2 more per box than before.

56 7 = 8 (pcs).

8-6=2 (pcs).

A: There are 8 pcs per box, and now there are 2 more pcs per carton than before.

56 divided by 7=8, so now 8 per box;

8-6=2, so now there are 2 more per box than before.

Now there are 56 7 = 8 per box.

More per box than the original: 8-6=2 (pcs).