Webinars SET B - Grade 9-10 - Sunday@6-7pm EST-Recording Webinar 7

Video Transcription

Video Summary

Lesson 7 introduces logical reasoning through a series of classic contest-style logic problems and highlights the importance of organizing information.<br /><br />It begins with a “question-only speakers” puzzle: residents ask only questions, either “positives” (questions with a “yes” answer) or “negatives” (questions with a “no” answer). By testing cases and using contradiction, the conclusion is that Albert is positive and Berta is negative.<br /><br />The lesson then surveys common logic problem types: logic grids, the pigeonhole principle, liar/truth-teller problems, and determining which statements are true or false. A key theme is that logic problems often look wordy, so the main skill is structuring information with tables, diagrams, notation, and variables.<br /><br />Several worked examples reinforce strategies:<br />- A boys/girls “solved vs. not solved” problem is solved by building a 2×2 table; it shows the number who solved equals the total number of girls.<br />- A “unique hair counts” problem uses smaller cases to detect a pattern, leading to a maximum of 2007 villagers.<br />- A liar/truth-teller group problem is solved by checking possible liar counts, yielding 6 liars.<br />- A handshake/graph problem (participants P1–P2016) is simplified to a smaller even case and generalized; P2016 shakes 1008 hands.<br />- A multiple-choice implication puzzle is solved by rewriting implications; only C can be the single correct answer.<br />- An arm-wrestling scheduling problem converts total plays into pairwise match counts to deduce Alice lost the second game.<br />- A word-scoring puzzle uses casework and constraints from Sam’s 19 points to find James scored 25.<br /><br />The lesson closes by emphasizing careful reading, extracting key facts, organizing data, using contradiction, and choosing efficient clues and strategies.

Keywords

logical reasoning

contest logic problems

logic grids

pigeonhole principle

liar and truth-teller

contradiction proof

truth values of statements

handshake problem

implication rewriting

casework and pattern finding