Solve a problem in the supplementary question .

Let the side lengths of the two rectangles be 5x, 4x, 3x, and 2x respectively, then 2(5+4)x-2(3+2)x=72

x=9, the side lengths are 45, 36, 27, 18, respectively, the area of the first rectangle is 90*72=1620cm 2, and the area of the second rectangle is 54*36=486cm2

Let the length and width of the first rectangle and the length of the second rectangle be 5x 4x 3x 2x, so that the circumference of the first rectangle is 18x, and the second is 10x, and then the column: 18x-10x=72 to get x=9 cm.

That is, the length and width of the first rectangle and the length and width of the second rectangle, in order of 45, 36, 27, 18 cm, can be obtained.

72 2 (5+4-3-2) = 9, the length and width of the first rectangle and the length and width of the second rectangle. 45, 36, 27, 18 in order

The area of two rectangles is 45*36=1620, and 27*18=486

Let the sides of the two rectangles be 5x, 4x, 3x, and 2x respectively.

5x+4x〕*2=〔3x+2x〕*2+72.The solution is: x=9 so the sides of the two rectangles are 45, 36, 27, 18

So the area of the two rectangles is 1620 cm and 486 cm respectively.

Question 3: A person who knows whether the number on his hat is divisible by a.

Know that the number of your hat is not divisible by a.

That is, only 5 of the 9 two-digit numbers are divisible by a.

So 5a<=99,6a>100

So a can only be taken in 17 19.

In the same way, a person who knows whether the number on his hat is divisible by 24 knows that the number of his hat is not divisible by 24.

Multiples of 24 have 24,48,72,96, and it stands to reason that 5 people should raise their hands, so it means that at least one person must know that they are divisible by 24, and it also shows that a can only be 18, because 72 in multiples of 24 can be divisible by 18 at the same time.

So: the two digits on the hats of the other 8 people are: 18, 36, 54, (72), 90, 24, 48, 96

So the sum is 438

17. Complete the following problem-solving process.

deb c (two straight lines parallel and equal at the same angle).

c 90° (known), deb 90° (equivalent substitution.

de bc (vertical definition.

Let the speed of this "Harmony" EMU be x kilometers per hour: 1280 x = 1280 (x

1280/x=4096/x-11

2816/x=11

x = 256 The speed of the "Harmony" EMU is 256 km/h.

This is a fractional equation solving problem.

If the speed of the ordinary train is x, then the speed of the EMU train is.

then you get 1280 x+1280

Solution x=80

then EMU speed.

If the speed of this "Harmony" EMU is x kilometers per hour, then the speed of the ordinary express train is x kilometers per hour. Columnable equations:

1280/(x/

x=256

Let the uphill road be xkm long and the flat road be ykm long, then there is the following binary linear equation x 3 + y 4 = 52 60

x/5+y/4=42/60

Solution: x= y=

There are uphill roads XKM and flat roads YKM. Column equations x 3+y 4=54 60, x 5+y 4=42 60

Then solve the system of equations x=,y=, so the whole process is x+y=

Let the uphill length be x and the flat road length be y, then, x 3 + y 4 = 54 60, x 5 + y 4 = 42 60, , x=, y=, x+y=, x+y=

If the slope distance is x km and the flat road distance is y km, then the whole journey from A to B is x+y km, and according to the known conditions, the system of equations: x 3 +y 4=54 60

y/4 +x/5=42/60

Subtract the two equations to get x 3-x 5=12 60 Solve x= Bring in the equation to get y = Therefore, x+y= the whole journey km from A to B

It's very simple, children have to be serious. I rely on others for everything. Do your homework yourself, be a good student.

If a bun is 1 yuan and a 20% discount is 8 jiao, buy three get one free is to spend 3 yuan to buy 4, and that one is yuan. Greater than A: When you buy 3, the boss lady is cheaper, and it is cheaper to buy a boss.

Solution: 1. From the parabola y=a(x+6) -3, we can know that the vertex d(-6,-3)de x axis gets de=3, and from ae=3de ae=3, we can get the coordinates of a point (-9,0) or (-3,0) and put it into the analytic formula 0=9a-3 to get a=1 3, so the analytic formula of this parabola: y=1 3x +4x+9

2. From the observation of the image, it can be seen that the point p that meets the requirements is only (-6,0).

3. (I haven't come up with a better way to solve this problem for the time being) if we make the point e third-divided line segment dn, because de=3m is in the second quadrant, then ne=9 can get n point coordinates (-6,6) from the Pythagorean theorem dm +nm =dn , let m(x,y),dm =(x+6) +y+3) ,nm =(x+6) +y-6) ), we can get (x+6) +y+3) +x+6) +y-6) =81 from the parabola y=1 3(x+6) -3 to get (x+6) =3y+9 substitution to obtain 3y+9+(y+3) +3y+9+(y-6) =81 to obtain y = 9, y = 3 or -3 because of the y = 3 taken in the second quadrant, substitute y = 3 into the analytic formula to obtain 3 = 1 3x + 4x + 9 to obtain x + 12x + 18 = 0 solution to obtain x = -2 + 3 times the root number 3 or -2-3 times the root number 3, because the m point in the second quadrant can only take x = -2-3 times the root number 3 to get m (-2-3 times the root number 3,3).

Answer: 1 (1 20 + 1 30) = 12

A did 16-3=13 days, i.e. 13-20

1-13 20) 1 30 = days.

The formula for the day synthesis:

16-[1-(16-3) 20] 1 30=Answer: B rested for a day

There is a problem with the second problem upstairs, it should be 2 solutions (-6,0)(-6,1).

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638 square decimeters = square meters square decimeters.

2 square meters 3 square decimeters = [square meters = square decimeters.

square decimeter = square meter square decimeter = square centimeter hectare = square meter square kilometer = hectare.

35 square centimeters, 150 hectares, square meters = square centimeters, square kilometers = hectares, square decimeters, = [square meters.

square decimeter = [square meter = square centimeter.

638 square decimeters = square meters square decimeters.

2 square meters 3 square decimeters = [square meters = square decimeters.

square decimeter = square meter square decimeter = square centimeter hectare = square meter square kilometer = hectare.