请教JJ27题的版本2，急...

jessica_cxy

27 

版本2：Sound track coding use 6 bit, each bit is either a number or a char，the order of the bit matters. Company T1 use [0-9] for the first 2 bits, and use A-Z excluing AEIOUY for the rest 4 bits. Company T2 use [0-9] for the first 4 bits, and use A-Z excluing AEIOUY for the rest 2 bits. What is the ratio of T1's total coding to T2's total coding

Note: (There are 20 chars when excluding AEIOUY)

答案都是 1/8,1/4,3/4 等等

hwzhang： T1有：10^2 * 20^4, T2: 10^4 * 20^2, ratio T1/T2 应该 = 4

关于版本2，我是用这种方法的：P(2)(10)* P(4)(20)/ P(4)(10)* P(2)(10)，但是无论如何不能算出4这个答案，请问这种方法对吗？谢谢阿！

蓝色回忆

题目没说数字和字母不可以重复，所以不能用P去算

jessica_cxy

谢谢!!