Florida B.E.S.T. MA.912.LT.4.10

MathGrades 9–12Develop an understanding of the fundamentals of propositional logic, arguments and methods of proof.

The Standard

Judge the validity of arguments and give counterexamples to disprove statements.

Florida B.E.S.T. Standards for Mathematics

Teacher's field guide

What Students Need to Do: Students identify the premises and conclusion in an argument, then check whether the reasoning guarantees the conclusion. They test broad claims by finding a single case that makes the claim false.
What Mastery Looks Like: Students can separate premises from a conclusion and decide whether the conclusion must follow. They can disprove a universal claim with one example that meets the conditions but not the conclusion.
Common Misconceptions: Students may think an argument is valid whenever its conclusion is true. They may also give an example that supports a claim instead of one that proves the claim false.
How to Assess It: Use this exit ticket: “All multiples of 4 are even. 18 is even. Therefore, 18 is a multiple of 4.” Ask students to judge the reasoning and explain why.

Lesson moves

Give groups premise and conclusion cards, then have them build valid arguments and identify combinations where the conclusion does not follow.
Ask students to explain why a true conclusion does not always make an argument valid, using their own example.
Play Counterexample Challenge, where pairs draw universal claims and earn a point for finding a valid counterexample within one minute.
Analyze claims from advertisements, polls, or social media posts, identifying assumptions and testing whether the stated conclusion follows.

Free download

$Preview of the MA.912.LT.4.10 printable worksheet$

A ready-to-print activity worksheet aligned to MA.912.LT.4.10, with an answer key for the teacher on its own page. No account needed.

PDF, US Letter, prints cleanly in black and white.

Keep exploring

Grade, subject, topic, and the complete standard are prefilled. Create one free, no account needed.