🧩 Logical Reasoning
Use clues to deduce answers step by step
🧩 What is logical reasoning?
Logical reasoning means using clues to figure things out step by step. You don't guess — you eliminate what's impossible until only the answer remains.
📋 Strategy: Process of elimination
Example: Nine cards (1–9) face down. Four people pick two cards each:
- Alan: "My numbers add to 6" → could be (1,5) or (2,4)
- Bart: "Difference is 5" → could be (1,6), (2,7), (3,8), (4,9)
- Cora: "Product is 18" → could be (2,9) or (3,6)
- Dane: "One is twice the other" → could be (1,2), (2,4), (3,6), (4,8)
Now work through the constraints: If Cora has (2,9), then Bart can't have any pair with 2 or 9. Bart could have (3,8). Then Alan can't have 3 or 8, so Alan has (1,5). Dane can't have 1,2,3,5,8,9 so Dane has (4,??) — but 4 and 8 won't work (8 taken). Try Cora = (3,6) instead... keep going until everything fits!
🏃 Strategy: Work the chain
For ordering/ranking problems, build the chain one clue at a time.
Example: Six children in a race:
- Ariadne is 3rd → ___, ___, Ariadne, ___, ___, ___
- Biel is 6th, just behind Ernest → Ernest is 5th
- Fatima is between Ariadne (3rd) and Ernest (5th) → Fatima is 4th
- Diana overtook Charles at the finish → Diana is ahead of Charles
- Remaining spots: 1st and 2nd for Diana and Charles → Diana 1st, Charles 2nd
⚖️ Strategy: Balance and weight clues
When you know a dog + 1 puppy = 14 kg and a dog + 2 puppies = 18 kg:
The difference (18 − 14 = 4) is exactly one puppy's weight. So each puppy = 4 kg, and the dog = 14 − 4 = 10 kg.