What is the probability that a seven-digit phone number contains the number 7?

Answer 1

Okay first you can't have a 1 or 0 leading...The number of items without 7 = 7*9^6

Total number of seven digit phone numbers = 8*10^6

1 - first #/second # = 0.535

Answer 2

There is a 1 in 9 chance that each of the seven digits in the phone number could be a 7. So, 1/9 multiplied by 7 is your answer. The 7 comes from the 7 different numbers in the phone number. The 1 in 9 comes from: each number could be a 1, 2, 3, etc, 8, or 9.