what is the probability that a 6 digit phone number contains at least one 8?
3 answers
The U.S. has no six-digit phone numbers.
must be an old-type "crank on the wall" from The Waltons era ....
anyway ....
I will assume that none of your 6 digit numbers can start with a zero, and that numbers may be repeated,
so we can't have a number with no 8
prob of no 8
= 8 x 9^5/(9x10^5)
so prob that it contains at least one 8
= 1 - (8x9^5)/(9x10^5)
= appr 0.475
anyway ....
I will assume that none of your 6 digit numbers can start with a zero, and that numbers may be repeated,
so we can't have a number with no 8
prob of no 8
= 8 x 9^5/(9x10^5)
so prob that it contains at least one 8
= 1 - (8x9^5)/(9x10^5)
= appr 0.475
I remember back to the 1940s in Chicago. Our first phone number was Regent 2642. It was changed to RE 4-2642. After that it was the 7-digit number.