Question

Bank of America customers select their own three-digit personal identification number (PIN) for use at ATMs. zero can be the first digit and the numbers can be repeated, what is the probability Mr. Jones and Mrs. Smith select the same PIN?

Answer 1

Mr jones and smith select the same pin is 9*10*10=900

Answer 2

10 digits
0,1,2,3,4,5,6,7,8,9

can be repeated

3 numbers
10^3=1000
1/1000 that bob gets a certain pin

1/1000 that jill gets a certain pin

so multiply them
(1/1000)(1/1000)=1/1,000,000

probablity is 1/1,000,000