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Locating Legs

Locating Legs

This week’s Puzzle Corner activity has a holiday theme. In it, students are presented with a paradoxical scenario and asked to try to make sense of it. In this scenario a child is hiding under a table at her parent’s holiday party. Looking out, she can count 20 legs and thus knows there are 10 adults in the room. A little while later, all the adults move to another room, yet the girl is still able to see six legs. The challenge is to determine how this is possible.

Students may come up with some very creative solutions to this puzzle, and that should not be discouraged. For example, they might say that she could see three adults in the other room through and open door, or three children come into the room, or that she can see an insect crawling on the floor under the table. These explanations are fine, since they show students are creative in their attempts to solve the paradox. There is, however, a fairly straightforward solution to this puzzle.

Lucy is hiding under a table at her parent’s holiday party. Looking out, Lucy counts 20 legs in the room. Later, all 10 adults leave the room. However, Lucy can still see 6 legs. How is this possible?

Table

Solution

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The puzzle describes a little girl hiding under the table at her parents’ holiday party. She looks out and counts 20 legs, so she knows that there are 10 adults in the room. When the adults all leave and go to another room, she can still see six legs. The explanation is that she still sees her own two legs and the four legs of the table that she is hiding under.

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