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Logical reasoning · lesson 27 of 30 · free

Number puzzles — Logical reasoning for kids

Magic squares, “I am a 2-digit number …” riddles and consecutive numbers all have one answer. Turn every clue into a small sum and the answer pops out.

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How to think it through

Clues into sums — “each clue is a small sum; together they leave only one number”

  1. Magic square: find the total from a full row, column or diagonal, then fill the gap.
  2. Digits that add to S and differ by D: the bigger digit is (S + D) ÷ 2.
  3. Three consecutive numbers: the middle one is the sum ÷ 3.

Use it for: Number puzzles in Olympiads and maths clubs, and early algebra thinking.

Worked example: I am a 2-digit number. My digits add up to 11 and my tens digit is 3 more than my ones digit. What number am I? → 74

  1. Tens digit = (11 + 3) ÷ 2 = 7.
  2. Ones digit = 11 − 7 = 4, so the number is 74.

Check: 7 + 4 = 11 and 7 − 4 = 3 ✓

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✏️ Practice

Work it out in your head or on paper, type the answer and press Check. Stuck? Press “Show me how”.

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🏁 Lesson 27 test

20 questions. Check each answer, then go to the next one. Get 16 or more right to pass.

🏅 Sign in with Google to earn the 🧩 Puzzle Pro badge when you pass — and a certificate when you finish all 10 lessons of Part 3 · Logical thinking. You can still take the test without signing in.

🖨️ Number Puzzles Worksheet

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