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Two coins that make thirty cents

riddlelogicreading-carefullyclassic

You have two US coins that add up to 30 cents. One of them is not a nickel.

What are the two coins? (US coins: penny 1 cent, nickel 5, dime 10, quarter 25, half-dollar 50.) Many people declare the puzzle impossible; explain exactly which word they are misreading.

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The statement says one of them is not a nickel. It says nothing about the other one.

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The theory behind this question.

Cheryl's Birthday and Iterated KnowledgeLogic and QuantifiersOne Question, Two Guards, One DoorProof Techniques: Direct, Contrapositive, ContradictionAdaptive Versus Pre-Committed Weighing Strategies

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