A certain telephone number has seven digits. If the telephone number has the digit zero exactly 3 times, and the number 1 is not used at all, what is the probability that the phone number contains one or more prime digits.  Choose the correct choice from the following choices.
A) 1/24  B) 1/16  C) 1/2  D) 15/16  E) 23/24
First step of getting rid of 3 digits of containing zeros is right: we are left with 4 digit number each of which can be one of 8 digit (2,3,4,5,6,7,8,9 as 0 is already used in first three and 1 is not used).   Next step:   total number of combinations possible 8^,   combinations with NO PRIME 4^4,   P(no prime)=4^4/8^4=1/2^4   P(p&gt;=1)=1-1/2^4=15/16   Answer 15/16.
<result>D</result>
A certain telephone number has seven digits. If the telephone number has the digit zero exactly 3 times, and the number 1 is not used at all, what is the probability that the phone number contains one or more prime digits.