Unit 15 · Truth and Lie Logic
Finn, Grace and Harriet — Find the Truth-Teller
Lesson 2 of 2
Truth-table puzzles reward one habit: assume each person won, mark every statement true or false, and drop anyone with two falses in their pair.
“At most one false per person” grids appear on Selective TS in the harder band — fast elimination once you test winners systematically instead of guessing.
The examiner checks whether you can test each candidate winner, count falses per row, and find the only scenario where nobody breaks the one-false rule.
Three people each make two statements about who won. Exactly one winner exists. No person may have more than one false statement in their pair.
Best approach: Test Finn, then Grace, then Hana as winner. For each trial, tick ✓/✗ on all six statements. Two ✗ in one row → reject that winner immediately. The survivor is the answer.
Question
Three students — Finn, Grace, and Hana — each entered the school art competition. The judge confirms that exactly one of them won first prize. Each student makes two statements about who won. Some statements are true and some are false. However, no more than one statement in each student's pair is false.
| Finn | Grace | Hana |
|---|---|---|
| Grace won first prize. | Finn won first prize. | Grace won first prize. |
| I did not win first prize. | Hana won first prize. | Finn did not win first prize. |
Based on the given information, which one of the following statements must be true?
Select an answer to see the explanation.
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