Geometry · Chapter 1 · Lesson 1.5 · Printable PDF · Free

Conjecture, and Why a Pattern Is Not a Proof Worksheet with Answer Key

8 problems on conjectures and why a pattern is not a proof: testing claims, counting toothpick and angle patterns, searching for counterexamples, and telling for-every claims from there-is claims. 3 pages, with a worked answer key and a one-page lesson handout. Free to download, no sign-in.

8 problems3 pagesanswer keylesson handout
Printable Conjecture, and why a pattern is not a proof worksheet with answer key - Geometry (Page 1 PDF preview)
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What's on the worksheet

  1. Say how each piece of news changes the status of an open conjecture.
  2. Count toothpicks in rows of squares, state a conjecture for n squares and test it.
  3. Settle claims about the distance from the origin to points on a line.
  4. Test a prime number conjecture and explain why it implies a claim about odd numbers.
  5. Find the angle of regular polygons and test a whole number of degrees conjecture.
  6. Check a last digit claim for n from 0 to 9 and explain why ten checks are enough.
  7. Decide if each claim is a for-every or there-is claim and what each fact settles.
  8. Show a quadrilateral is a counterexample to a conjecture about equal diagonals, then test a repair.

Teach it first

The free lesson teaches it with worked examples and practice problems.

Conjecture, and why a pattern is not a proof: the lesson ›