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
Please explaine your answer.
since order matters, use permutation.
= 10p5/10p4 = [(10x9x8x7x6x5!)/5!]/[(10x9x8x7x6!)/6!) = 6