GurooHow to multiply numbers close to 100 in your head
Numbers just below 100 have a beautiful shortcut. Instead of a long multiplication, you work with how far each number is from 100.
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Download the free worksheet (PDF)
Worksheet includes an answer key for grown-ups
How it works
- Find how far each number is below 100 (the gaps).
- Take one gap away from the other number. That is the first part.
- Multiply the gaps. That is the last two digits.
Worked example
97 × 98: the gaps are 3 and 2. 97 − 2 = 95. 3 × 2 = 06. Answer: 9506.
Top tip
Always write the last part as two digits: 96 × 97, gaps 4 and 3, gives 93 and 12, so 9312.
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