Help please?

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1 Answer

See below:

Explanation:

a

With 5 digits and all of them can be any one of 10 digits (0-9), there are:

#10^5=100,000# different passwords that can be made. And so the probability of his guessing the password on his first try is:

#1/(100,000)=0.00001=0.001%#

b

If digits aren't allowed to repeat, then the first place can be any one of 10 digits, the second place any one of 9 remaining digits, etc., giving:

#10xx9xx8xx7xx6=30,240# different passwords. And so the probability of his guessing on his first try is:

#1/(30,240)~=0.000033=0.0033%#