[求助] 数学题

6               Six different numbers are to be selected from the (0,1,2,3,4,5,6) to compose a 6-digit even number that is greater than 300,000. How many such integers are there?

1680

谢谢

算了半天。。刚算出来。。

当百万数位3和5时，个位数有4种可能0,2,4,6,剩下4位数的可能情况加以来为5*4*3*2。。总共可能性为2*(4*5*4*3*2)=960

当百万数位4和6时，个位数有3中可能，剩下4位数的可能情况加以来为5*4*3*2。。。总共可能性为2*(3*5*4*3*2)=720

960+720=1680