2．如果＝3，＝2是方程的解，则＝　　　　　 .

1. 在方程＝5中，用含的代数式表示为＝　　　 ；当＝3时，＝　 .

3、第二卷为主观试题，共13小题，满分55分。

2、第一卷为客观试题，共15小题，满分45分。

13.The probability of winning a single game of chance is 0.15, and whether or not the game is won is independent of any other game.

a. Suppose Georgia plays the game 20 times. Find the probability of her winning two or three times to 3 diecmal place.

(2　 marks)

b. Suppose Georgie plays another sequence of n games. If the probability of winning at least one prize is more than 0.95, then find the smallest value n.

(2　 marks)

c. Suppose Georgie plays another sequence of n games.If the probability of winning at least two prizes is more than 0.95, then find the smallest value n.

(2　 marks)

12.Suppose that the number of people in a random sample of 20 people who prefer Pepsi over Coca-Cola is a binomial random variable with a mean of 5 and a variance of 3.75. Find the probability that more than five people in a sample of size 20 prefer Pepsi to 3 diecmal place.

(2　 marks)

11.The following graph shows two binomial random variables, X (plotted with a ‘+’) and Y (plotted with a ‘°’). Suppose that the parameters of the variable X are nx and px, and the parameters of the variable Y are ny and py. From the graph it can be seen that:

(　　　　　　　　　　 (2　 marks)

10. Suppose that X represents the number of black balls in a sample of size 14 drawn (withreplacement) from a large urn containing 70 balls. If Var(X) =, then find the number of black balls in the urn

(2　 marks)

9.Suppose that 48% of people in a certain population wear glasses, and that groups of 50 people are chosen at random from this population. We would expect that the approximate number of people who wear glasses in 95% of such groups would be from　　　　　　　　　　　　　　　

　　　　　　　　　　　　　　　　　　　　　　　　　　　 (2　 marks)

8.Suppose that X is a binomial random variable with mean 　　and standard deviation . Then find the probability of success.

　　　　　　　　　　　　　　　　　　　　　　　　　　　 (2　 marks)