Ask everyone about the fourth grade math Olympiad problem and say it, thank you

First of all, these questions need to use Byck's theorem, so let's first briefly understand the relevant knowledge of Byck's theorem.

Grid polygons and Biker's theorem, and a prerequisite for the application of Biker's theorem, is grid polygons. There are two cases for lattice polygons.

Case 1: Grid polygons in a square grid <>

As shown in the figure above, on a piece of paper, draw some horizontal lines and some vertical lines, and make any two adjacent parallel lines equal in distance (usually 1 unit), so that a grid of squares is formed on the paper, and each intersection point is called a grid point.

In a square grid, a rectilinear polygon drawn with lattice points as vertices is called a lattice polygon.

The lattice polygon in this case is suitable for the first formulation of Biker's theorem.

Biker's theorem formulas 1 <>

As shown in the figure above, if n is used to represent the number of lattice points inside the polygon, l is the number of lattice points on the polygon boundary, and s is the area of the polygon, we can find the following rule, which is Biker's theorem's theorem)。Yess=n+l/2-1

Case 2: Grid polygons in a regular triangle mesh <>

As shown in the figure above, on a piece of paper, first draw some horizontal lines and some straight lines with an angle of 60 to the horizontal straight lines, and make the distance of any two adjacent parallel lines equal, so that a network of regular triangles is formed on the paper (usually the area of each small regular triangle is 1), and each intersection point is called a lattice point.

In this case, the lattice polygon is governed by the second formulation of Byck's theorem.

In a regular triangle network, a linear polygon drawn with lattice points as vertices is called a lattice polygon.

Biker's theorem formulas 2 <>

As shown in the figure above, if n is used to represent the internal lattice points of the polygon, l is the lattice points on the boundary of the polygon, and s is the area of the polygon, which is similar to Biker's theorems=2n+l-2

No, I think these math problems are very difficult and beyond the scope of my logical thinking.

I can't do it, because there are many elementary school math Olympiad problems that are very difficult, and I have graduated for many years, and I have forgotten this knowledge.

I can't do it, because the fourth grade Olympiad is very difficult to do, and there are a lot of things to consider, and I also have strong thinking skills, so I can't do it.

Yes, because I also learned a lot of ideas to solve problems when I was older, so I should be able to solve the Olympiad problems in elementary school.

Take a thick line (thicker than the short side of the figure), start from the bottom left corner and draw it to the top right, cover the short side, and you have two triangles.

This is a two-force question.,I've seen it in the post bar for a long time.,That's the answer.。 By the way, there is no width in the straight line.

1. According to the question to mean c=b 2b=a-160，a=4c。Obtained from a=2b, then b=160.

So a=320, c=80 a+b+c=560。2. Set up B to build x meters.

Then A is 2x and C is, so A is 800 and C is 160. 3. Set the second rope to be left x meters. Because the two ropes are the same length, it is 18+3x 26+x

x=4.The original length = 26 + 4 = 30, and the two are the same. 4.

Let the divisor be xThe dividend is 2xThere is 2x+x=212-2.

The divisor x=70 is divided by 140. 5.It's good to draw a picture of this question.

A has 25*2+8 58 more than B, B has (800-58) 2=371, and A has 371+58 429. 6. Set up after X years. (43+x) (11+x) 3,x 5 7.

2x+x+x+300=1900.B x = 400, A 2 x 800, C x + 300 700 8.

Let B be x=12 A=2*12+4=28 C 3*12+2=set X A. B is 4+2+1= x 6 more than A, and A is 1310. Set x sheets of five yuan.

10*3x+5x=175 x=5。15 pieces of 10 yuan.

I'm the one above with a slight smile. I'm sorry, just the tenth question is the last question, and now I'll give you the special answer to the tenth question. This question is best drawn, he has science and technology books, story books, and other books, 58 + 42 + 60, you will find that these three books are added twice each, then (58 + 42 + 60) 2 80 is the total number of books he has, 80-42 = 38, which is the number of science and technology books!

There are so many questions, and there are still 0 points on the books, which is insincere

A is 4 times that of C, and B is 2 times that of C, so A is 2 times that of B. Because car B is 160 kg less than car A, A is 320 kg, B is 160 kg, C is 80 kg, a total of 560 kg.

1 All A is faster than B, and when A arrives on the same side as B, A sees B, which means that the distance between the two must be less than 100 meters.

A's velocity is 50 meters per minute, B's velocity is 42 meters per minute, and their distance shrinks by (50-42)*1=8 (meters) per minute

When A sees B, their distance is shortened by at least 200-100=100 (meters) and the time it takes is 100 8 = min).

Because A sees B, it must be on the same side, and the earliest time is when A has just turned, and the time it takes A to walk from one vertex to the next is 100 50=2 (minutes).

In units of 2 minutes, the minimum time greater than a minute is 14 minutes, so 14 minutes after the two people set off, A can see B for the first time.

100 meters on each side, 200 meters apart. If you want to see, at least 100 meters away from each other.

50-42=8 A walks 8 meters more than B per minute. Then 100 8 = 50 minutes * one lap plus half a lap plus 25 meters.

42* One lap plus one imposes 25 meters.

You can add a picture, just walk another 75 meters to see B for the first time; Then A walked 625 + 75 = 700 meters.

700 50 = 14 minutes.

1 117

5 Too lazy to count.

10 can't do . . .

s is equal to (first term, last term) The number of items divided by 2

The last term is equal to the first term + (number of items - 1) * difference.

I do it with a formula.

I drew a line, but I don't know if it's right.

I'm also speechless......But it's the big thick line ...... in your head

After the swap of chickens and rabbits, there are 100-92 = 8 fewer feet.

It turns out that there are 8 (4-2) = 4 more rabbits than chickens.

Chickens: (100-4 4) (4+2) = 14.

Rabbits: 14 + 4 = 18 pcs.