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Ponder This

December 2000

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Ponder This Challenge:

A man leaves his office every day at 5:00, takes the commuter train and arrives at his hometown depot at 6:00. His wife arrives at the depot at 6:00, in their car, and drives him home. This is everyday procedure.

One day, he leaves his office at 4:00 instead of the usual 5:00, neglects to inform his wife, and arrives at the depot at 5:00 instead of 6:00. He decides to walk home. On the way home he meets his wife, who is driving to pick him up at the usual 6:00. He gets in the car, they drive home and arrive 20 minutes earlier than usual.

Question 1: How long, in minutes, did he walk?

Question 2: What unstated assumptions went into your answer to Question 1? What could go wrong?

We won't be posting a list of solvers this month, but we will post some of the submitted answers for Question 2, starting December 8.

Part 1 originally appeared in a Martin Gardner column (which we were unaware of when we printed the puzzle)

We will post the names of those who submit a correct, original solution! If you don't want your name posted then please include such a statement in your submission!

We invite visitors to our website to submit an elegant solution. Send your submission to the

If you have any problems you think we might enjoy, please send them in. All replies should be sent to:


Challenge: 12/01/00 @ 9:00 AM EDT
Solution: 12/08/00 @ 9:00 AM EDT
List Updated: 12/01/00 @ 9:00 AM EDT

People who answered correctly:

(No list this month, selected answers to question 2 will be posted starting on December 8th)

Attention: If your name is posted here and you wish it removed please send email to the