Three pets, three children, and three clues to match them.
The big ideaA logic puzzle is solved by using clues to rule out what cannot be.
How it works
A logic puzzle is solved by using clues to rule out what cannot be.
A grid helps. A tick means yes, and a dot means no, so that pair is ruled out.
Each clue rules some things out, and clues lead to more clues. Whatever is left must be true.
A good puzzle has exactly one answer, so you never need to guess or peek.
Two clues from Gran's puzzle.How to solve a puzzle.
Example 1: Clue one
Sam's pet has no fur, and only the fish has none.
So Sam has the fish.
Tick Sam and the fish, and put dots for Sam and the cat, and Sam and the dog.
Example 2: Clue two
Ada's pet does not bark, and dogs bark.
So Ada cannot have the dog.
The fish is already Sam's, so only the cat is left for Ada.
Example 3: What is left
Sam has the fish, and Ada has the cat.
The dog is the only pet left.
It must be Leo's.
Example 4: A clue that does not follow
Someone says: Ada's pet does not bark, so it must be the fish.
Not barking only rules out the dog.
Ada's pet could be the cat or the fish, so one more clue is needed.
Example 5: The bikes
Leo, Ada and Sam have blue, green and yellow bikes. Sam's is not blue and not green, so Sam's is yellow.
Leo's bike is the color of a clear sky, so it is blue.
Ada's is the green one that is left. Every clue agrees.
Words to know
clue
A fact that helps you work something out.
rule out
Cross out something that cannot be.
grid
A table that keeps track of what is true.
tick
Marks a pair that must match.
dot
Marks a pair that is ruled out.
Watch out
Not barking only rules out the dog. It does not say the pet is the fish.
Each child has one pet, so a clue about one pet does not add a second pet.
Each pet has one owner, so when Sam has the fish, Ada cannot have it too.
Guessing, peeking and copying skip the thinking. The clues are enough.
Try it
Sam's pet has no fur. Which pet is it?
Sam has the fish and Ada has the cat. Whose pet is the dog?
Ada's pet does not bark. Do you put a tick or a dot for Ada and the dog?
How many answers should a good logic puzzle have?
True or false: guessing solves every puzzle.
Answers: 1. The fish · 2. Leo's · 3. A dot · 4. Exactly one · 5. False
Try at homeWith a grown-up, make a puzzle about three people and three snacks. Write three clues and see if your grown-up can solve it with a grid of ticks and dots. Check that exactly one answer fits.
For grown-upsMake a three-clue puzzle together about three people and three snacks. Write the clues and see whether you can solve it with a grid of ticks and dots, then check that exactly one answer fits.
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