John wrote a phone number on a note that was later lost. John can remember that the number had 7 digits, the digit 1 appeared in the last three places and 0 did not appear at all. What is the probability that the phone number contains at least two prime digits?
Choices
A) 15/16	B) 11/16	C) 11/12	D) 1/2	E) 5/8
XXXX(1}{1}{1}   X can be a prime number or non prime number   Prime number:2,3,5,7   Non prime-4,6,8,9(1 is already taken)   Probability(X is a Prime number)=4/8=1/2   Probability(X is a non-prime number)=4/8=1/2   So,Atleast 2 prime numbers=P P NP NP=4!/2!2!*1/2*1/2*1/2*1/2=6/16   Three prime numbers and one Non prime=P P P NP=4!/3!*1//2^4=4/16   All prime=PPPP=1/16   Total=11/16.   Answer:11/16
<result>B</result>
John wrote a phone number on a note that was later lost. John can remember that the number had 7 digits, the digit 1 appeared in the last three places and 0 did not appear at all. What is the probability that the phone number contains at least two prime digits?