KA-0091Elimination grids
4 points, difficulty 2 of 3Level 3–4about 90sAna, Bo and Cal each keep a different pet: a cat, a dog and a fish. Ana does not keep the cat. Bo keeps neither the cat nor the fish. Who keeps the cat?
Hints
Take them one at a time. The first gives nothing away.
1A nudge
Draw a three-by-three grid and cross boxes out.
2The strategy
People down the side, pets across the top. Every clue crosses a box out, and every tick crosses out the rest of its own row and column.
3The full solution
Bo has neither cat nor fish, so Bo has the dog. Ana has no cat and the dog is taken, so Ana has the fish. Cal is left with the cat.
Solution— no shortcut on this one
Draw the grid. Bo's clue crosses out cat and fish for Bo, leaving only dog - so tick Bo and dog, and cross dog out for everyone else. Ana's clue crosses out cat for Ana, and dog is now gone, so Ana has the fish. That leaves the cat for Cal. The transferable idea: every tick immediately crosses out the rest of its row and its column, and that is where most of the progress comes from.
Why this is on the test: Matching puzzles are pure bookkeeping, and the grid is what stops a student holding four facts in their head and dropping one.