The recording played a gunshot inside it. If the man committed suicide, he wouldn't have been able to stop the recording after he pulled the trigger.
When the professor confirmed Johnny's anonymity (the professor didn't know who he was), Johnny quickly slipped his exam paper into the pile of exams and ran off, so the professor wouldn't know which exam paper deserved an F. Congratulations on sticking through the whole riddle.
If the man committed suicide, he would've left the window open and you wouldn't have had to open it.
5 minutes. We can assume that one chicken is placed in each microwave and that each chicken takes 5 minutes to cook.
The police told him to get to the crime scene, but they didn't specify where. The husband couldn't have known where the crime scene was unless he'd been there when the wife was dead or dying.
47 days. Whatever day the lily pads covered half the pond, the whole pond would be covered the next day.
Joe's birthday is on December 31, the last day of the year. The current day was January 1st of the next year.