Current location - Training Enrollment Network - Mathematics courses - Hello, teacher, I'm playing with my mobile phone, because I thought of a math problem: How many ways are there for the 9-cell password of an ordinary smart phone, that is, there must be 9 points?
Hello, teacher, I'm playing with my mobile phone, because I thought of a math problem: How many ways are there for the 9-cell password of an ordinary smart phone, that is, there must be 9 points?
This problem is complicated and can be solved by enumeration. Find the total number of four points first, then five points until the last nine. Finally, add up all the results. The acupoints in Jiugongge can be divided into three categories according to their relative positions: the first category is the acupoints on the side, with four acupoints; The second category is the point on the corner, 4 points; The third category is the center point, there is only one. When linking, it should be noted that two endpoints on the same side cannot be connected if the midpoint of that side is useless, that is, if two endpoints on the same side are to be connected, the midpoint of that side must be used. The sides here include four sides of a square, two sides of a middle cross and two hypotenuses. Due to the limitation of this link condition, the calculation of the total number of links in Jiugongge is more complicated. If you use a computer to do exhaustive work, you can quickly find out the total. The order of magnitude is 1 ten thousand to 1 ten thousand.