[求助]TT数学第一套第26题

newaaron

    

Running
at their respective constant rates, machine X takes 2 days longer to produce w
widgets than machine Y.  At these rates,
if the two machines together produce 5/4 w widgets in 3 days, how many days
would it take machine X alone to produce 2w widgets?

    

A.     
4

    

B.     
6

    

C.     
8

    

D.     
10

    

E.     
12

我怎么算都是6，答案却是8，望高人指教。谢谢！

newaaron

这个题也望NN指点指点：

    

Q25:

    

A
photographer will arrange 6 people of 6 different heights for photograph by
placing them in two rows of three so that each person in the first row is
standing in front of someone in the second row. 
The heights of the people within each row must increase from left to
right, and each person in the second row must be taller than the person
standing in front of him or her.  How
many such arrangements of the 6 people are possible?

    

 

    

A.     
5

    

B.     
6

    

C.     
9

    

D.     
24

    

E.     
36

    

newaaron

第一题答案看错了，应该是E,离我算的更远了，不知道怎么回事儿。

生活就是越狱

我第一题算出来也是E。第二是不是A呢？

newaaron

强，你两个都作对了。第二个是A