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: 6Dodecahedron: 35Icosahedon: 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. The 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 
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
 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?
雨点在离地10米时和即将落地时的下落速度是一样的. 根据这一点你觉得雨点是否受到空气的阻力? : 雨点受到了空气的阻力.不然的话, , 雨点在即将落地时的下落速度应该大于离地10米时的下落速度.
 求压力Three cylinders labeled A, B, C, are all at the same temperature. The volumes of the containers are 2.0 L, 4.0 L, and 6.0 L, respectively. Cylinder A contains 0.679 grams of neon gas at a pressure of 120 mmHg, cylinder B contains 2.45 grams of nitrogen gas at a pressure of 210 mmHg, and cylinder C is completely empty at the start. If the contents of A and B were completely transferred to C (assuming ideal conditions), what would the pressure become in cylinder C? (A) 0.25 atm (B) 180 mmHg (C) 330 mmHg (D) 675 mmHg (E) 1980 mmHg?
答案是B
参考解题过程:
温度不变，压强与体积成正比例相关。 采用气体分压和总压来做：总压＝分压1+分压2  neon gas 来说，体积由2变6,增大了两倍，即变为原来的3倍，气压变为原来的三分一：120*(1/3)=40  nitrogen gas 来说，体积由4变6,增幅为二分一，即为原来的二分之三，气压变为原来的三分之二:210*(2/3)=140 40+140 ＝180

几道典型初中英语数理化试题的英语作答.doc