第1个回答 2013-02-21
56×1.02-1.4×0.8=7×8×1.02-7×0.2×8×0.1=7×8×1.02-7×8×0.2×0.1=56×1.02-56×0.02=56×(1.02-0.02)=56;
7.2×14.5-17×2.8=7.2×14.5+17×(10-7.2)=7.2×14.5-7.2×17+170=170-7.2×(17-14.5)=170-7.2×2.5=170-1.8×(4×2.5)=170-18=152;
256×254/255+254/255=(255+1)×254/255+254/255=254+254/255+254/255=254+2×(255-1)/255=254+2-2/255=255又253/255;
2.4×20又3/5+33.1×7.6=2.4×20.6+33.1×(10-2.4)=331-2.4×(33.1-24.6)=331-3×(0.8×12.5)=331-3×10=301;