The symbol（符号） 5！is called five factorial（阶乘）and means 5×4×3×2×1；Thus（因而）5！=120．How many 6！=？What is the result of 

(n-1)!

n!

？Do you know 6！=； 

(n-1)!

n!

=？．

阅读对话从每题ABCD四个选项中选出一个最佳答案完成对话。
A: Good morning.     1  
B: Yes , please .I ’d like to buy a tie for my brother.
A:     2   
B: Blue. My brother likes blue best.
A: How about this one?
B: Oh, it’s very nice. __  3    
A: 50 yuan.
B: That’s too expensive. I can’t afford it.    4   
A: Yes. This light blue one is only 30 yuan.
B: Well, this one looks very good. And the price is OK.    5  
【小题1】A Can I help you?
B What’s wrong?
C How are you?
D Would you like something?
【小题2】A What’s his job?
B How old is he?
C What color do you want?
D What size do you want?
【小题3】A What about that one?
B How much is it?
C How many are they?
D What do you think?
【小题4】A I want another one.
B Please show me the light one
C How much is the lighter blue one?
D Do you have any cheaper ones?
【小题5】A I will take it.
B I won’t buy it.
C I can’t believe it.
D I don’t think so.

阅读对话从每题ABCD四个选项中选出一个最佳答案完成对话。
A: Good morning.     1  
B: Yes , please .I ’d like to buy a tie for my brother.
A:     2   
B: Blue. My brother likes blue best.
A: How about this one?
B: Oh, it’s very nice. __  3    
A: 50 yuan.
B: That’s too expensive. I can’t afford it.    4   
A: Yes. This light blue one is only 30 yuan.
B: Well, this one looks very good. And the price is OK.    5  
【小题1】A Can I help you?
B What’s wrong?
C How are you?
D Would you like something?
【小题2】A What’s his job?
B How old is he?
C What color do you want?
D What size do you want?
【小题3】A What about that one?
B How much is it?
C How many are they?
D What do you think?
【小题4】A I want another one.
B Please show me the light one
C How much is the lighter blue one?
D Do you have any cheaper ones?
【小题5】A I will take it.
B I won’t buy it.
C I can’t believe it.
D I don’t think so.

阅读对话从每题ABCD四个选项中选出一个最佳答案完成对话。
A: Good morning.     1  
B: Yes , please .I ’d like to buy a tie for my brother.
A:     2   
B: Blue. My brother likes blue best.
A: How about this one?
B: Oh, it’s very nice. __  3    
A: 50 yuan.
B: That’s too expensive. I can’t afford it.    4   
A: Yes. This light blue one is only 30 yuan.
B: Well, this one looks very good. And the price is OK.    5  
【小题1】A Can I help you?
B What’s wrong?
C How are you?
D Would you like something?
【小题2】A What’s his job?
B How old is he?
C What color do you want?
D What size do you want?
【小题3】A What about that one?
B How much is it?
C How many are they?
D What do you think?
【小题4】A I want another one.
B Please show me the light one
C How much is the lighter blue one?
D Do you have any cheaper ones?
【小题5】A I will take it.
B I won’t buy it.
C I can’t believe it.
D I don’t think so.