To how many patrons could a telephone company furnish numbers having five digits, the first digit not being zero? I know the answer is 90,000 im just wondering how to do it

Answer:90,000Step-by-step explanation:GivenA Company has to provide 5-digit numbers(The first digit≠0)This question can be solved with Permutations and CombinationsAssume there are 5 blank spaces representing any phone numberThe first digit can be filled in 9 ways(excluding 0 ={1,2,3,4,5,6,7,8,9})The second digit can be filled in 10 ways(no exemptions={0,1,2,3,4,5,6,7,8,9})The third digit can be filled in 10 ways(no exemptions={0,1,2,3,4,5,6,7,8,9})The fourth digit can be filled in 10 ways(no exemptions={0,1,2,3,4,5,6,7,8,9})The fifth digit can be filled in 10 ways(no exemptions={0,1,2,3,4,5,6,7,8,9})So total number of ways to fill the 5 blanks [tex]=9\times10\times10\times10\times10\\=90000[/tex]⇒Total number of 5-digit phone numbers= 90000