Category Archives: Multiplication via Fractions

Multiply with fractions as an approximation

Suppose we want to do 27 * 77 (30-3)*(70+7) = 30(1-3/30)70 (1+7/70) = 30*70 (1-1/10)*(1+1/10) = 2100 * (1- 1/100)= 2100-21= 2079 It won’t always be this nice. 27*73 = 2100 (1-1/10)(1+3/70) (1-1/10)(1+3/70)= 1-1/10+3/70-3/700 -1/10+3/70 = (-7+3)/70 = 4/70 4/70 … Continue reading

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