Math · Stage 3
Reason about truth-tellers and liars for consistency
On Logic Island a truth-teller always tells the truth and a liar always lies — try each possibility and keep the one where every statement fits.
✦ Math📘 Stage 3 · S3⏱ ~10 min🧒 Ages 7–8★ Free to start
I can reason about statements from truth-tellers and liars, testing each possibility for consistency to find who is telling the truth.
📖
Kavi on Logic Island 🏝️
Kavi lands on Logic Island 🏝️, where every person is either a truth-teller (always true) or a liar (always false). "How do I know who to believe?" hoots Kavi. "Easy — I try a guess, then check every sentence. If one sentence doesn't fit, my guess is wrong. The guess where everything agrees must be the answer!"
🎓
What your child will learn
1Two kinds of peopleEveryone on Logic Island follows one rule forever. A truth-teller only ever says true things. A liar only ever says false things — every single time. Tap a row.
2Some sentences give no clueNot every sentence helps. Tap each card and see why.
3Test each possibilityGuess who is telling the truth, then check if every sentence fits.
4True words or false words?Each kid makes one claim. You know the real fact in brackets. Sort each kid into Truth-teller or Liar.
🔍
A peek inside
The basket really has 6 pencils. Ivy says 'There are fewer than 10 pencils.' Is Ivy a truth-teller or a liar?
check against the fact: 6 is fewer than 10 → her sentence is TRUE
Try this at home: A truth-teller always says ______ things; a liar always says ______ things.
Ready to play and learn?
Start the free interactive lesson, or print the handout for screen-free play.
Part of Math · Stage 3 · S3 on KAVI Academy — a secular, whole-child learning platform for ages 5–12.