The first question is the Egyptian pyramid of khufu. It is mentioned in the title that its shape can be regarded as a regular quadrangle, and the area of a square whose height is the side length of the quadrangle is equal to the area of a triangle of the quadrangle. What is the ratio of the height of the base of a triangle to the length of the bottom square? This problem is a three-dimensional geometric problem. If you want to do it right, you can draw a sketch in the examination room. It doesn't need to be particularly precise. You can understand. After all, the examination time is the most important, such as the following one.
In fact, this problem is not too difficult. As long as you understand the problem, you can list the equations. The first equation uses Pythagorean theorem, and the second equation uses area equality. To simplify the calculation, we can set the base length of the regular pyramid to 2. Here, why should it be set to 2? It can actually be set to 1, 4,? Numbers, x, b can be used, because the final result is a ratio, and whatever you set will eventually be discarded. If you look at the topic again, you can see that it is easiest to set the side length to 2, because half of it is exactly 1, and the square of 1 will be 1 in the later calculation, which can save a lot of calculation time. As a multiple-choice question, don't make trouble for yourself, just give an answer quickly. Finally, after combining the above two formulas, we can get a quadratic equation with one variable. There are two solutions after solving, one is negative, and then it is 2 longer than the above, which is the correct answer C! There are two difficulties in this problem, one is whether you can draw a graph, and the other is whether you can list the above two formulas and solve them.
Next, the fourth question in the selected text of the second volume of the country is about the Temple of Heaven. Finally, how many pieces are there in the three-layer * * * sector plate? The college entrance examination is really difficult, but don't be too anxious about the exam. You must take the time to read the questions carefully and make clear the relationship between them. Even the wrong answers in the four options of the college entrance examination questions are not given casually. Some students asked me if I had miscalculated just now, and there were wrong answers in the options. What a coincidence? This is no coincidence. When setting the four options, the teacher has considered what the students may have miscalculated and what the answer may be.
Let's start looking at this problem. Let's look at the top floor first. The first ring is 9 yuan. If you add 9 yuan per lap, the second lap should be 18 and the third lap should be 27. This is a arithmetic progression with an error of 9, and the sum formula Sn is as shown above. This summation formula does not explain too much. Suppose you see that the students here have learned all the high school knowledge. Because the number of rings in each layer is the same, the number of slates in the second ring should be the second big circle minus the first small circle, that is, S2n-Sn. Similarly, the number of slabs in the bottom ring should be the third big circle minus the second big circle, namely S3n-S2n. These three formulas constitute arithmetic progression's secondary conclusion with an error of n^2d. It should be easy to remember if you do more problems, and it doesn't matter if you don't do them. Therefore, from the meaning of the problem, it can be concluded that 729= tolerance = n 2D, d=9, and n=9, that is, a * * * has nine cycles. Then we add up the three formulas to be 3402. In fact, you can completely flatten the Temple of Heaven and regard it as three concentric circles on the plane, which is S3n itself. So the answer to this question is 3402, and it is difficult to choose C. Personally, I think it is more difficult than the pyramid. Did you do this problem correctly?