Brain Teasers, a.k.a. The RTFQ Quiz by LuskT

Question 11

A clock chimes the number of the hour every hour, and once at 15-minute intervals. If you just heard the clock chime once (and have no other way to check the time), what is the longest you may have to wait to be sure what time it is?

90 minutes (12:15 to 1:45)