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2.8 1.7 4.5简便计算

2.8*1.7*4.5=28/10*17/10*45/10=14/5*17/10*9/2=14*17*9/(5*10*2)=2142/100=21.42 求采纳

//b.jpg" esrc="http&nbsp.com/zhidao/pic/item/64380cd7912397dd509ed9475f82b2b7d1a2878a.jpg" target="_blank" title="点击查看大图" class="ikqb_img_alink">蓝天|来自:百度作业帮|发布于2015-09-14 11:37评论

2.6*【(1.7+2.8)\4.5】=2.6*【4.5\4.5】=2.6*1=2.6

用脱式计算2.8*1.7*4.5=4.76*4.5=21.42

2.8*4.5+7.2*4.5=4.5x(2.8+7.2)=4.5x10=45

2.8x1.7x4.5=21.42 运用拆分法将2.8分为3-0.2,通过计算得:2.8x1.7x4.5=(3-0.2)x1.7x4.5=3x1.7x4.5-0.2x1.7x4.5=3x1.7x4.5-0.9x1.7=1.7x0.9x(3x5-1)=1.7x0.9x14=1.7x14x(1-0.1)=(2-0.3)x14x(1-0.1)=(28-4.2)x(1-0.1)=28-4.2-2.8+0.42=28-(4.2+2.8)+0.

2.8*1.7*5÷1.7=2.8x5x(1.7÷1.7)=2.8x5=14

2.8x1.7÷2.8x1.7=2.8÷2.8x1.7x1.7=1x1.7x1.7=2.89

-3.5-(-1.7)+2.8-5.3=-3.5+1.7+2.8-5.3=(1.7+2.8)-(3.5+5.3)=4.5-8.8=-4.3

7.2+2.8x4.5=7.2+12.6=19.8

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