SOLUTION: a certain town can use the digits 0, 1, 2, 3, 7, and 9 for it's telephone prefixes. how many 3-digit telephone prefixes are possible for this town if each digit can be used only on

Question 358378: a certain town can use the digits 0, 1, 2, 3, 7, and 9 for it's telephone prefixes. how many 3-digit telephone prefixes are possible for this town if each digit can be used only once in a prefix and the first digit cannot be a 1 or a 0?
Answer by edjones(8007) (Show Source): You can put this solution on YOUR website!
nPr=permutations of n things taken r at a time.
6P3=120 Think of the 120 as 6 columns of 20 three digit numbers whose initial number stays the same throughout each column and that the columns beginning with 0 and one are not allowed.
120 * 4/6 = 80
.
Ed
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