one bead stands for 5one bead stands for 1( a picture of an abacus )How can you do calculations(计算)quickly? These days, you can easily use a calculator. But how about people in ancient times? In the very beginning, the cleverest among them thought of using stones and seashells. Then...
of the first calculating machines was an abacus.Abacuses are so fast and accurate that people still use them today.On the abacus in the picture,the beads on the wires represent ones,tens,hundreds and thousands starting from the bottom wire.The picture on the right shows a ...
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Calculatingmachines Oneofthefirstcalculatingmachineswasanabacus.Abacusesarefastandaccurate,sopeoplestillusethemtoday.Ontheabacusinthepicture,thebeadsonthewiresrepresentones,tens,hundredsandthousandsstartingfromthebottomwire. Now,weusemoderncalculators.Thepictureontherightshowsamoderncalculator.Itcanadd,subtract,...