2.4*5.8+0.28*4.2简便算法
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2.4*5.8+0.28*4.2简便算法
199.7*19.98-199.9*19.96
199.7*19.98-199.9*19.96
![2.4*5.8+0.28*4.2简便算法](/uploads/image/z/19010900-20-0.jpg?t=2.4%2A5.8%2B0.28%2A4.2%E7%AE%80%E4%BE%BF%E7%AE%97%E6%B3%95)
2.4*5.8+0.28*4.2=2.4*(5.8+4.2)-(2.4-0.28)*4.2=24-2.12*4.2
=24-2.1*4.2-0.02*4.2=24-8.82-0.084= ...
199.7*19.98-199.9*19.96
=0.001*(1997*1998-1999*1996)
=0.001*[(1998-1)*1998-(1998+1)*(1998-2)]
=0.001*[-1998-(-1998-2)]
=0.002
=24-2.1*4.2-0.02*4.2=24-8.82-0.084= ...
199.7*19.98-199.9*19.96
=0.001*(1997*1998-1999*1996)
=0.001*[(1998-1)*1998-(1998+1)*(1998-2)]
=0.001*[-1998-(-1998-2)]
=0.002