Tutorial 126 |
Multiplying two 2-digit numbers (difference of 3)
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- Choose a 2-digit number.
- Select a number either 3 smaller or 3 larger.
- Add 1 to the smaller number, then square.
- Subtract one from the smaller number.
- Add this to the square.
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Example:
- If the first number is 27, choose 24 as the second number.
- Add 1 to the smaller number: 24 + 1 = 25.
- Square this number: 25 × 25 = 625.
- Subtract one from the smaller number: 24 - 1 = 23.
- Add this to the square: 625 + 23 = 648.
- So 27 × 24 = 648.
See the pattern?
- If the first number is 34, choose 31 as the second number.
- Add 1 to the smaller number: 31 + 1 = 32.
- Square this number: 32 × 32 = 1024.
- Subtract one from the smaller number: 31 - 1 = 30.
- Add this to the square: 1024 + 30 = 1054.
- So 34 × 31 = 1054.
Choose the second number that will give you the easier square, and use your square
shortcuts.
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