Question 1 of 5
Mental multiplication - free strategyWhat is 49 x 51?
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The factors sit one below and one above 50, so use 50 x 50 and adjust by 1 x 1.
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Use a difference of squares
For 49 x 51, treat the factors as 50 - 1 and 50 + 1.
- Use (a - b)(a + b) = a squared - b squared.
- 50 squared is 2,500.
- Subtract 1 squared: 2,499.