几道典型初中英语数理化试题的解答
英语数学题:  expected number
An ant and a blind spider are on opposite corners of a cube. The ant is stationary and the spider moves at random from one corner to another along the edges only. What is the expected number of turns before the spider reaches the ant? Optional: Also solve for a square, octahedron, icosahedron, and dodecahedron.
Answer
The answer is 10.
If the spider started at a corner diagonally on the same face as the ant the answer would be 9, and if the spider started at an adjacent corner the answer would be 7.
Here are answers for other figures:
Square: 4
Octahedron: 6
Dodecahedron: 35
Icosahedon: 15
初中英语数学题 求r的解法
If you drew a dot on the edge of a wheel and traced the path of the dot as the wheel rolled one complete revolution along a line, then the path formed would be called a cycloid (shown above), combining both forward and circular motion. What is the length of the path formed by one complete revolution? Assume the wheel has a radius of 1.
Answer    The answer is 8r, where r equals the radius of the wheel.
The distance as the dot moves from the 3:00 to 9:00 postion counterclockwise is 4*21/2. As it moves from the 9:00 position to the 3:00 position the distance is 8- 4*21/2, assuming the r=1.
初中英语数学题   求N的解法
Given n points drawn randomly on the circumference of a circle, what is the probability they will all be within any common semicircle?
Answer
For n points the answer is n/(2n-1).
初中英语数学题   4道排列组合问题
1.To keep computer files secure, many programs require the user to enter a password. Th
e shortest allowable passwords are typically six characters long and can contain both numbers and letters .How many six-character passwords are possible if (a)characters can be repeated and (b) characters cannot be repeated?
2.A relay race has 4 runners who run different parts of the race. There are 16 students on your track team. In how many ways can your coach select students to compete in the race?
3.Your school yearbook has an editor-in-chief and an assistant editor-in-chief. The staff of the yearbook has 15 students. In how many ways can students be chosen for these 12 positions?
4. Auditions are being held for the play shown. How many ways can the roles be assigned if (a) 6 people audition and (b)9 people audition?
看下面给的信息。
Parts available:
student A, student B, Principal, Teacher, Librarian, Coach
semicircle
英语物理题   距离
Light with a wavelength of 500nanometters strikes a double slit with a spacing of 0.4mm. An interference pattern is observed on a screen 2 meters away. How far from the center of the screen in millimeters is the first bright line?
明纹位置x=nLλ/d
第一个明纹x=Lλ/d=2*500*10^(-9)/0.4*10^(-3)=2.5*10^(-3)
所以距离中心2.5毫米处
初中英语：英语物理试题 空气的阻力
The speed of falling rain is the same 10m above ground as it is just before it hits the ground.What does this tell you about whether or not the rain encounters air resistance?

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