一道ＧＷＤ的排列组合

tayleerchen2

How many different 6-letter sequences are there that consist of 1 A, 2 B’s, and 3 C’s ?   （Ｂ）

 

 

A.     6

B.     60

C.     120

D.     360

E.      720

我列的是Ｐ（６.６），错了，我是不是题意理解错了啊

tayleerchen2

还有一道：

Of the 2,500 tons of ore mined daily at a quarry, 0.4 percent results in a certain pure metal.  In how many days of mining will the total amount of pure metal produced at the quarry be equal to the daily amount of ore mined? 

 

 

A.          10

B.        100

C.        250

D.        400

E.      1,000

tayleerchen2

谢谢各位了, 第二道我连问题都看错了, 真是太粗心鸟,怪不得算死了都算不出来哦!