TED-ED: Can you solve the counterfeit coin riddle? - Jennifer Lu

The video tutorial presents a problem where the viewer, as the kingdom's greatest mathematician, must identify a counterfeit coin among twelve using a balance scale and only three weighings. The tutorial explains a strategic approach to solve the problem by dividing the coins into piles, using a marker to track results, and employing logical reasoning to narrow down the possibilities. The process involves initial and advanced weighing techniques to determine the fake coin, which is either slightly heavier or lighter than the others. Successfully identifying the counterfeit coin earns the mathematician freedom from the dungeon.

What is the main challenge presented to the protagonist by the Emperor?

• To negotiate a peace treaty with a neighboring kingdom

• To solve a complex mathematical equation

• To identify a counterfeit coin among twelve using a balance scale

• To escape the dungeon using a secret passage

How many coins are initially placed on the balance scale in the first weighing?

• Eight coins

• Four coins

• Two coins

• Twelve coins

What should be done if the first two piles on the scale do not balance?

• Mark the heavier side with a minus and the lighter side with a plus

• Mark the heavier side with a plus and the lighter side with a minus

• Mark all coins with zeros

• Remove all coins and start over

What is the purpose of reassembling the piles after the initial weighings?

• To remove ambiguity and identify the counterfeit coin

• To ensure all coins are weighed equally

• To make the process more challenging

• To confuse the Emperor

If the previously heavier side becomes lighter after substitution, what does it indicate?

• The remaining plus coin is the counterfeit

• The scale is malfunctioning

• The remaining minus coin is the counterfeit

• One of the three minus coins moved is the counterfeit