## Help me solve this maths riddle!!!

John forgot to bring his house keys with him,so he must use secret numbers to open his house door.But he reasiled that he totally forgot the numbers,despite of that,he still insisted using the secret numbers. When he got there, he came to a combination lock on the door, with the dial numbers going from 0 to 59. Unfortunately, he forgot whether there were three or four numbers in the combination, or even which direction to turn the wheel!

If it takes him 15 seconds to try a single combination, how many days will it take him to to try every possible combination? Please round to the nearest day.

 From 0 to 59, that are 60 possibilities, I assume? (is that including or excluding 0 and/or 59?) 60^3 possibilities with 3 numbers. 60^4 possibilities with 4 numbers. 60^3+60^4=13176000 possibilities 13176000*15=197640000 seconds=3294000 minutes=54900 hours=2287.5 days.
 Recognitions: Gold Member Science Advisor Staff Emeritus I just saw exactly the same question on "math message board" except that it was phrased in terms of a bank robber trying to open a vault!

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