Study guides › Level 6 · Master

What must be true?

Level 6 · for questions like “There are some blims, some glorps and some zats. All blims are glorps. No glorps are zats. Which must be true?”

💡 The idea

The words are made up on purpose, so only the facts count, not what you already know. Picture each word as a circle of things.

🪜 The steps

1. “All A are B”: draw circle A inside circle B.
2. “No A are B”: draw A and B apart.
3. “Some A are B”: the circles overlap.
4. Every group has members, so no circle is empty.
5. A choice must be true only if it is true in every drawing that fits the facts.

⚠️ Watch out

• “All A are B” does not mean “All B are A”. All cats are animals, but not all animals are cats.
• “Could be true” is not the same as “must be true”.
• “No A are B” and “No B are A” say the same thing. So do “Some A are B” and “Some B are A”.

🎯 Try these

1. All plinks are dobs. All dobs are mivs. Must all plinks be mivs?
2. All wugs are tavs. Some tavs are frobs. Must some wugs be frobs?

Answers: 1) Yes 2) No: the frobs could be among the tavs that aren’t wugs

This guide is also in the 10LogicQ app: tap “📖 Study guide” after a puzzle.