Brute Force - Part Two

Assuming it's a three digit number and it takes my 5 seconds to dial and listen if the call went through, the average time would guess the number would be: ((5 seconds)/(1 guess))*((1000 possibilities)/(2)) is 2,500 seconds or 41 minutes.

Unfortunately, the worst case scenario is the correct one.  The emergency number is 999, so the time it would take would be ((5 seconds)/(1 guess))*(1000 Possibilities) = 5,000 seconds or 1 hour and twenty three minutes.