Spot the Pattern in the 9 Times Table
The tens digit is one less than the other factor, and the two digits add to 9.
9 times a number is almost 10 times that number, one group short. 9 × 7 = 10 × 7 − 7 = 70 − 7 = 63. That is why the tens digit is one less than the other factor, and why the two digits of the product add to 9.
For 9 × 7, take one less than 7. That 6 is the tens digit. The ones digit has to make 6 + ? = 9, so it is 3. Read the digits: 63. The pattern and the subtraction say the same product.
- Take one less than the other factor. That is the tens digit.
- Choose the ones digit so the two digits add to 9.
- Read those two digits as the product.
- Or subtract the other factor from 10 times itself, if you would rather.
9 × 4: tens digit 3, ones digit 6, because 3 + 6 = 9. The product is 36. Check: 40 − 4 = 36. 9 × 8: tens digit 7, ones digit 2, product 72. Check: 80 − 8 = 72. 9 × 6 is 54, because 5 is one less than 6 and 5 + 4 = 9.
Watch out
- Using the other factor itself as the tens digit. It has to drop by 1.
- Making the digits add to 10 instead of 9.
- Forgetting this pattern is only for multiplying by 9.
What is 9 × 8?
Tens digit 7, ones digit 2, because 7 + 2 = 9. The product is 72. Also 80 − 8 = 72.
What is 9 × 3?
Tens digit 2, ones digit 7, because 2 + 7 = 9. The product is 27. Also 30 − 3 = 27.
Math practice for 9 Times Table
Multiply by 9
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