Call a number a digital number if it consists of all the digits from 1-9, each used exactly once. What is the probability that a digital number will be divisible by 7 ? What is the probability that a digital number will be of the form 9p, where p is a prime?
Digital Numbers using all digits from 1-9
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elementary-number-theory
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1The funny thing about digital (or pandigital) numbers is that they are all multiples of 9. – 2012-08-30