Math PicnicEvery sheet is a promise

The quadrilateral hierarchy, step by step

Every square is a rectangle.

Practice Practice sheetNew questions
The question

Every parallelogram is a rectangle.

Every parallelogram is a rectangle.

Every parallelogram is a rectangle.
alwayssometimesnever
alwayssometimesnever
sometimes
  1. Before trying anything, notice what each answer would COST. One example that works proves nothing at all. One that fails rules out "always" on its own. They are not the same size of evidence.
  2. So hunt for a counter-example — a case where the claim breaks. That is the cheapest question to ask, and its answer decides between all three.
  3. Try a 6 by 6 square — true. Try a slanted rhombus with 13-unit sides — false. One example is not enough. So the answer is sometimes.

How it works.

  1. 01

    Before trying anything, notice what each answer would COST. One example that works proves nothing at all. One that fails rules out "always" on its own. They are not the same size of evidence.

  2. 02

    So hunt for a counter-example — a case where the claim breaks. That is the cheapest question to ask, and its answer decides between all three.

  3. 03

    Try a 6 by 6 square — true. Try a slanted rhombus with 13-unit sides — false. One example is not enough. So the answer is sometimes.

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