Can you solve the counterfeit coin riddle? - Jennifer Lu
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TED-Ed Animation lessons feature the words and ideas of educators brought to life by professional animators. Are you an educator or animator interested in creating a TED-Ed Animation? Nominate yourself here »
Meet The Creators
- Educator Jennifer Lu
- Director Outis
- Script Editor Alex Gendler
- Associate Producer Jessica Ruby
- Content Producer Gerta Xhelo
- Editorial Producer Alex Rosenthal
- Narrator Addison Anderson
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To make the problem simpler, for example, we can reduce the total number of coins to 9. To further simplify, we can reveal whether the counterfeit is lighter or heavier at the onset, as is shown here. For a harder version of the problem, start with 39 coins and four weighs.
In all cases, the counterfeit coin riddle offers a fun introduction into the world of deductive reasoning.

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About TED-Ed Animations
TED-Ed Animation lessons feature the words and ideas of educators brought to life by professional animators. Are you an educator or animator interested in creating a TED-Ed Animation? Nominate yourself here »
Meet The Creators
- Educator Jennifer Lu
- Director Outis
- Script Editor Alex Gendler
- Associate Producer Jessica Ruby
- Content Producer Gerta Xhelo
- Editorial Producer Alex Rosenthal
- Narrator Addison Anderson