The new school year had barely started when I got a call from a friend who is an elementary school principal. She told me that every morning she announces the names of students who are celebrating a birthday. "One student noticed that we've already had two days on which no student has a birthday," she said. "With 900 students in the school, she thought that at least one birthday should be announced every day. She wants to know more about the math for this situation." What a great question! Th...
