A few math problems about the junior high school, a math problem for the junior high school

1.If the ratio of the radius of the bottom surface of a cone to a cylinder is 1:2, and the ratio of height is 2:3, then the ratio of their volumes is (1):18).

and b are both natural numbers not less than 1, and if a-b = 27, then the minimum value of the product of ab is (28).

and b are both two-digit integers, and a:b=5:3, then b is maximum (57).

4.There is a cup of brine, the ratio of salt to water weight is 1:4, after adding 6 grams of salt, salt accounts for 1 3 of the weight of the brine, this cup of salt water turned out to be (30) grams.

5.Cut a 2 8 8 (in centimeters) box down from the top of a cube and cut off the box.

The volume is the volume of the remaining box (1/3).

6.There were 49 students visiting the Botanical Gardens. The ticket is 10 yuan for one person, and 80 yuan for each ticket for 10 people, and they need to buy tickets at least (400) yuan.

7.The three inner angles of a triangle are not equal, the smallest of which is 45°, and this triangle must be (d).

a.Isosceles triangle bRight triangle cObtuse triangle dAcute triangle.

The first question above is wrong, hehe, I did it faster than me, but unfortunately the volume of the vertebral body was not multiplied by 1 3

At the same time, the distance traveled by the gray wolf and the pleasant goat is more than:

If the distance of the gray wolf running 3 steps is regarded as the unit "1", then the gray wolf is 1 3 (one-fifth) per step, and the pleasant goat is 1 4 per step, and their distance ratio is: (1 3 4) :(1 4 5) = 16:15

If the distance for the gray wolf to catch up with the pleasant goat is x meters, then there is:

10/x=（16-15）/16

x==160

The size of each step of the gray wolf is 4 3 times the size of the joyful yang.

And the speed of the gray wolf is only 4 5 times that of the pleasant goat.

Let the time be y, so 4 3 * 4 5y = 1 * 1 * y + 10y = 150 The distance run by the gray wolf is 4 3 * 4 5 * 150 = 160 (m).

The speed ratio of the gray wolf to the pleasant goat is 16:15

The distance difference is 10 meters, 10 ((16-15) 16) = 160 meters.

I don't know how many meters each step of Gray Taro and Pleasant Goat is?

Set the single digit x ten digit y

10y+x) = (x+y) squared.

And because the power of 9 is equal to the square of 27.

x+y=910y+x=27

x=7y=2

Question 1 answer 11 (3 numbers are Question 2 answers 5 and 18 or 2 and 45 Question 3 answer 2:5 34 = 4 5:17 Question 4 (kg Yuan Question 5 1280 kg Question 6 Question 7 6 and 3/5 Question 8 Question 9 108 175 lz points should be given to me, I have done n for a long time, after all, n years have not been done, I even forgot the definition, and I also helped you check the dictionary.

1.11 (they consist of 2, 3, 6).

2.18 and 5, 9, and 10 (they are negative meaning, no one can divide the other) 3 34：17=2:1

4.(Kilograms.)

5.1280 kg.

1.The sum of three different numbers is 11 and 2These two numbers can be 2 and 45 or 5 and 18 3

Question 1:1

This is a simple question, assuming that the reciprocal of the three numbers is 1, x, -x (x is any natural number), so that the reciprocal sum can be 1

So the original number is 1,1 x,-1 x,so the sum is still 1 The second question: 1 and 90,2 and 45 (there are many others) This problem actually does not have a lot of skills at all, but because it is a mutual quality (I am a few grades higher than you, I have looked up this term for a long time, I have forgotten it for a long time), and because their least common multiple is 90, it can be imagined that the product of the two numbers is 90, so you can start from 1.

For example: 1 90 = 90, 1 and 90 are coprime, which is desirable.

2 45 = 90, 1 and 45 are coplasmic, desirable.

3 30 = 90, but 3 and 30 are not coprime and are not desirable. And so on.

There's something to do, I'll add it in two days, I'm sorry.

Thinking about the whole of the two days, A traveled the whole way, B traveled 60 90 = 2 3, and there is still 1-2 3 = 1 3 The road does not travel, it takes hours, and it takes 4 3 1 3 = 4 hours for B to complete the journey.

The distance between the two places is 60 4 = 240 km.

When I saw this problem, my head was clouded.

Let the distance between a and c = x kilometers, and the distance between b and c = y kilometers, then ab distance = x + y

When passing through point C, car B arrives 10 minutes earlier than car A; x/90-y/60=10/60 2x-3y=30

Car A arrives 1 and a half hours earlier than car B when passing through C, x 60-y 90 = 3x-2y = 270

Subtract the two formulas: x+y=240

Method 1:

Let the first time of car A from A to C be x hours, the time of the second time of car B from A to C is y hours, and the distance of AB is Z

90x+60（x-1/6）=z

60y+90（

90x=60y

60（x-1/6）=90（

x=5/3,y=5/2,z=240

AB distance 240 km.

Method 2: Set the AC distance to x and the BC distance to Y.

They are: x 90) - (y 60) = (1 6).

x/60)-(y/90)=(3/2)

Simultaneous equations, solved:

x=150y=90

then ab=x+y=240

Method 3: Set the AC distance to x and the BC distance to Y, on the first day, car A is 90*10 60=15 kilometers away from place C when car B arrives at place C, and car B is 60*km away from place C when car A arrives at place C on the second day, (x-150) 90=y 60

x-90)/60=y/90

Simultaneous equations, solved:

x=150y=90

then ab=x+y=240