1: 1/2 1/2 200/457
2: 36÷18=2 2×4=8
3: 3+2.8=5.8
4: 图一 3.14×22÷2 =3.14×4÷2 =6.24 图二 ﹙10+20﹚×﹙10÷2﹚÷2 =30×5÷2 =75 10×5÷2 =25 75--25=50
5: 1-1/2-1/4-1/8-1/16-1/32 =1-﹙1-1/2﹚-﹙1/2-1/4﹚-﹙1/4-1/8﹚-﹙1/8-1/16﹚-﹙1/16-1/32﹚ =1-1+1/2-1/2+1/4-1/4+1/8-1/8+1/16-1/16+1/32 =1/32
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