On the first day of school the History teacher is murdered. There are four suspects: the landscaper, a math teacher, a basketball coach, and the principal.

The landscaper said he was outside mowing the lawn.

The math teacher said he was giving a mid-year test.

The basketball coach said he was running practice drills with his players.

The principal said she was in her office.

After the alibis were given the police immediately arrested the murderer. But who?

Answer: The math teacher is the murder. His alibi says he was giving his students a mid-year test, yet it was only the first day of school.