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January 2022

Selected from: One Minute Mysteries: 65 Short Mysteries You Solve With Math!

 

Setting the Date

Birthday Cake

One night, Elijah and Kevin were watching the debate for the upcoming presidential election. They were in Kevin’s family room taking notes about the topics that were being discussed and the main points each candidate was making. There was going to be a quiz on the debate in their social studies class the next morning.

 

Kevin’s younger brother, John, was sitting at the computer in the corner, working on the invitations for his birthday party, which was going to be on January 6th. He always had his party on the actual day of his birthday, even if it was a school day. He was getting excited about it already, even though it was more than two months away.

 

 

Kevin had helped him get started on the computer program, but had to move over to the TV when the debate came on.

 

 

John read aloud what he had written so far:

 

 

“You are invited to a party for John’s birthday on . . . something, January 6th. Kevin, what day of the week is my birthday going to be? We don’t have a calendar for next year yet.”

 

 

“How should I know?” Kevin said. “I’m trying to watch this debate.”

 

 

“Do you remember what day of the week your birthday was on earlier this year?” Elijah asked John.

 

 

“Sunday,” John replied. “I remember we watched a pro football game on TV during the party.”

 

 

“Well, then shouldn’t it be obvious which day of the week your next birthday will be?” Elijah asked.