Magic number patterns — Maths trick for kids

The trick

Spot the pattern — “find the small fact, then grow it”

1. 37 × 3 = 111, so 37 × (3 × k) is k written three times.
2. 12345679 × 9 = 111111111, so 12345679 × (9 × k) is k written nine times.
3. 1 × 8 + 1 = 9, 12 × 8 + 2 = 98, 123 × 8 + 3 = 987 …; and 11 × 11 = 121, 111 × 111 = 12321.

Use it for: Amazing your friends, checking big multiplications, and learning to look for patterns before you calculate.

Worked example: 37 × 15 = 555

✏️ Practice

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

🏁 Trick 9 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 🌈 Pattern Painter badge when you pass — and a certificate when you finish all 5 tricks of Part 2 · Number magic. You can still take the test without signing in.

🖨️ Magic Number Patterns Worksheet

• Worksheet set 1 (PDF)
• Worksheet set 2 (PDF)
• Worksheet set 3 (PDF)