Figure showing method for multiplying 1223 (left) by using 20 counters on lined reckoning board. From Raymond Lull Practica Compendiosa Artis, 1523.

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Keywords: 20, 1223, 1523, arithmetic, artis, board, calculation, compendiosa, counters, figure, lined, lull, method, multiplying, numbers, practica, raymond, reckoning, showing, sums