Probability

Question

how many ways can a 7 digit number be dialed? Please help with full math

Answer 1

A seven digit number may be dialed, correctly, in only one way.

 

if someone were to ask how many 7-digit numbers are possible, that depends on the rules of telephone companies (for example, it may be that the leading digit must not be zero but other numbers are unrestricted.

When ANY number 0 through 9 may occuring any one of seven positions of a phone # then there are exactly 10^7 (ten million) possible phone numbers. Of course, this is not true, in reality.