Unary equations, help me solve them

Suppose the master brushes x m2 of the room in a day, then:

3x+40)*9=5*(x-30)*8 x=120

So 1The area of the wall that needs to be painted in each room = (3 * 120 + 40) 8 = 50

2.Total area = 36 * 50 = 1800 ; It takes 1800 (120+2*90)=6 days.

3.Set up hired master x people, apprentice y people.

Then: 3*(120x+90y)>=1800 means that the hired person should be able to do it in three days; (Equation 1).

x<=3 and an integer; (Equation 2).

y<=5 and an integer; (Equation 3).

Total wages payable = (85x+65y)*3

When x=0 is taken first, by Eq. 1, y>=, because y is max 5, so no, rounded off;

When x=1, by Eq. 1, y>=, because y is up to 5, so no, rounded;

When x=2, by equation 1, y>=4, so 4 and 5 can be taken, because the greater the y, the greater the salary, so discard the 5, y only take 4, the total salary = 1290;

When x=3, by Eq. 1, y>=, so 3 and 4 and 5 can be taken, because the greater y, the greater the salary, so discard 4 and 5, y only take 3, total salary = 1350;

From the above analysis, when x = 2 and y = 4, that is, when employing 2 masters and 4 apprentices, the total salary is the least, which is 1290, and can be completed within the specified three days.

Analyze the above floors on the third question:

The assumption on the 4th floor is wrong"Set up x hired masters and 8-x apprentices"No, it doesn't say that the total number of people to be employed is 8;

6th floor"According to the total area (x*120+y*90)*3=36*50"Wrong, I don't need the person I hire can only brush exactly 1800 square meters at the end of three days, but as long as it is done within three days and the total salary is the least, so this formula should be used"=.

I am close to full score in Shanghai science paper mathematics in the college entrance examination, if there is any mistake, please correct.

It's really easy.

Let's make a lot of images for yourself.

1. Set the area to s, (8*s-40) 3=9*s 5s=502, the speed of the master to brush the wall is 120, the apprentice is 903, the master is set to hire x people, and the apprentice is 8-x people.

The salary paid y = 3 * 85 * x + 3 * 65 * (8-x) = 60x + 1560 (x = 0 8) is an increasing function, take x = 0 when y is the minimum is 1560, all employ apprentices, not masters.

The first question is 50, the second question is 6 days, and the third question should be to hire 8 masters and 2 apprentices for 2 days.

The first two questions above are right, and the process is right, but the third question seems to be wrong, and the question doesn't say that you must work for 3 days.

v A: v B = 5:4, so t A: t B = 4:5, according to ab = bc to get that point b is the midpoint of the two places, let car A take the time x, then car B takes 11 - 7 + 4 = 8 minutes more than car A, according to the time ratio to list the equation t A: t B = 4: 5 = x:

x+8, the solution is x=32 minutes, so it took 32 minutes for A to complete the journey, and it took 40 minutes for B to complete the whole journey, because point B is the midpoint of the whole process, so the time taken by A to complete the half journey is 32 2 + 11 = 27 minutes, and the time taken by B to complete the half journey is 40 2 + 7 = 27 minutes, so when B walks to 27 minutes, A exceeds B.

Let the distance from A to C be S, and the speed of car A is V, then the speed of car B is, and car B starts 11 minutes earlier than car A, and the stopover is 7 minutes, which means that car B starts 4 minutes earlier than car A, and finally car A arrives 4 minutes earlier than car B, and if both cars start from A at the same time, car A is 8 minutes faster than car B. So the equation is as follows:

s, let the time of car A be t, then t=s v, so: t-t; The solution is t=32 minutes, and the time taken by car B is 40 minutes.

Point B is the midpoint of the whole journey, so the time it takes A to complete the halfway route is 32 2+11=27 minutes, and the time it takes B to complete the halfway route is 40 2+7=27 minutes, so when B walks to 27 minutes, A overtakes B.

1 (1 30 + 1 20) = 1 (2 60 + 3 60) = 1 * 60 5 = 12 (days).

To be able to fulfill the contract, it takes 12 days for two people to complete.

A walks more appropriately, and A's speed is slow.

Question 1 1 (1 30 + 1 20) = 12

So 12 days is enough.

Able to complete on time.

The second question (3 4) (1 30 + 1 20) = 75% before 9, it took 9 days.

If B is transferred, A still needs to spend.

1 4) (1 30) = days If 15 days are exceeded, B will need to spend more.

1 4) (1 20) = 5 days 5 + 9 = 14 days It is not exceeded, so it should be transferred away.

(1) The front team starts for one hour, 4 kilometers more rows, and the rear team needs 4 (6-4) = 2 (hours) to catch up, and it takes x hours to catch up, and the equation is:

6-4）x=4

x=2(2) ridden 12 2=24 (km).

Solution: It takes x hours for the rear team to catch up with the front team.

6x＝4（x＋1）

6x＝4x＋4

x 2 Since the liaison officer was riding non-stop when the last two teams did not catch up with the front team, he only stopped when the rear team caught up with the front team, so the liaison also traveled for 2 hours.

Hello, 8x=-2(x+4).

Remove parentheses, 8x=-2x-8

10x=-8

x=Solved.

1. Solution: X tons of seafood should be refined.

x/6+(140-x)/16=15

Solution: 8x+560-4x=720

8x-4x=720-560

4x=160

x = 40 (tons).

x7500 + 100x5000 = 800000 (yuan).