Ever wonder why alarm clock snooze alarms are 9 minutes? I did, so I did a little looking around, and come to find out its just so the only digit that has to be watched is the last digit, if the alarm goes off at 9:05 the longest time you can get just looking at the last digit is 9:14, if you did 9:25 the last digit would still be a 5 and the alarm would ring right away so 9 minutes allows for the longest allowed with just one digit being watched, and it allows me to learn how to multiply by 9 while half a sleep