简算(过程)3.48-1.79= 2273-665-348= 599996+49997+3998+407+89=100+
1个回答

100+99-98-97+96+95-94-93+.+8+7-6-5+4+3-2-1=(100-98)+(99-97)+(96-94)+(95-93)+.+(8-6)+(7-5)+(4-2)+(3-1)=2*50=100

3.48-1.79=3.5-0.02-1.8+0.01=1.69

2273-665-348=2270+3-660-5-350+2=1260

599996+49997+3998+407+89=600000-4+50000-3+4000-2+400+7+90-1=654487