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Multiplication algorithm
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====Examples==== This example uses peasant multiplication to multiply 11 by 3 to arrive at a result of 33. Decimal: Binary: 11 3 1011 11 5 6 101 110 2 <s>12</s> 10 <s>1100</s> 1 24 1 11000 ββ ββββββ 33 100001 Describing the steps explicitly: * 11 and 3 are written at the top * 11 is halved (5.5) and 3 is doubled (6). The fractional portion is discarded (5.5 becomes 5). * 5 is halved (2.5) and 6 is doubled (12). The fractional portion is discarded (2.5 becomes 2). The figure in the left column (2) is '''even''', so the figure in the right column (12) is discarded. * 2 is halved (1) and 12 is doubled (24). * All not-scratched-out values are summed: 3 + 6 + 24 = 33. The method works because multiplication is [[distributivity|distributive]], so: : <math> \begin{align} 3 \times 11 & = 3 \times (1\times 2^0 + 1\times 2^1 + 0\times 2^2 + 1\times 2^3) \\ & = 3 \times (1 + 2 + 8) \\ & = 3 + 6 + 24 \\ & = 33. \end{align} </math> A more complicated example, using the figures from the earlier examples (23,958,233 and 5,830): Decimal: Binary: 5830 <s>23958233</s> 1011011000110 <s>1011011011001001011011001</s> 2915 47916466 101101100011 10110110110010010110110010 1457 95832932 10110110001 101101101100100101101100100 728 <s>191665864</s> 1011011000 <s>1011011011001001011011001000</s> 364 <s>383331728</s> 101101100 <s>10110110110010010110110010000</s> 182 <s>766663456</s> 10110110 <s>101101101100100101101100100000</s> 91 1533326912 1011011 1011011011001001011011001000000 45 3066653824 101101 10110110110010010110110010000000 22 <s>6133307648</s> 10110 <s>101101101100100101101100100000000</s> 11 12266615296 1011 1011011011001001011011001000000000 5 24533230592 101 10110110110010010110110010000000000 2 <s>49066461184</s> 10 <s>101101101100100101101100100000000000</s> 1 98132922368 1 <u>1011011011001001011011001000000000000</u> ββββββββββββ 1022143253354344244353353243222210110 (before carry) 139676498390 10000010000101010111100011100111010110
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