The most obvious answer to a problem may be good, but it may not be the only one!
This is the Friday recitation. Mr. Mansa asks his students:
Which of the following numbers is not in the series?
2, 4, 5, 6, 8
It’s 5, that’s obvious! All the students find the right answer, except for Caboche, who says “I thought about it, but I prefer 4 because…”.
Mr. Mensa is not happy with the answer, so he deprives Caboche of recreation. He asks him to produce a text on the theme “I should have chosen 5”.
At first I thought of 5, because it is the only odd number.
But why not 8? It’s the only one with a completely closed line.
Then I thought of 2, replacing it by 7, we would have a nice sequence 4,5,6,7,8…
I looked at 6, but nothing came up. I turned it over and over in my head, then… Eureka! By turning the 6 over you get a different number. Nothing like that with the others.
Finally, I considered the 4. The 4 is the only number drawn with 2 lines. It is the only one without any curve. It is square. The others are not. It is also my favorite number: April 4 (it is the 4th month) is my birthday. For all these reasons, I chose the 4th.
Now I think I should have chosen the 5th, like everyone else.
After all, it’s the only one that can’t be added to any of the others to make 10: 4+6=10, 2+8=10…
Okay, I’ll take the 5!
The best answer to a problem is often the second one found. It shows that one is capable of creativity.
Stéphane Hamel is an experienced independent digital marketing and analytics consultant, innovator, educator and speaker with a keen interest for user privacy and ethical data use.
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I originally published this story on my blog in December 2003.
Reference for this story: “Défi mathématique, 1er cycle, #2,” Cheneliere/McGraw-Hill, Michel & Robert Lyons.