[Q. ] GWD PS
If a code word is defined to be a sequence of different letters chosen
from the 10 letters A, B, C, D, E, F, G, H, I, and J, what is the ratio
of the number of 5-letter code words to the number of 4-letter code words?
A. 5 to 4
B. 3 to 2
C. 2 to 1
D. 5 to 1
E. 6 to 1
請問為什麼這題不是5-letter code words=10!/(5)!*5! to 4-letter code words=
10!/4!*6!=6:5呢？
我不透這個解法為什麼是錯的
謝謝幫忙
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