72*2.07-1.8*3.6 和6.8*16.8+19.3*3.2

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72*2.07-1.8*3.6 和6.8*16.8+19.3*3.2
72*2.07-1.8*3.6 和6.8*16.8+19.3*3.2

72*2.07-1.8*3.6 和6.8*16.8+19.3*3.2
72*2.07-1.8*3.6
=3.6x20x2.07-1.8x3.6
=3.6x(41.4-1.8)
=3.6x(40-0.4)
=3.6x40-3.6x0.4
=144-1.44
=142.56
6.8*16.8+19.3*3.2
=6.8x16.8+(16.8+2.5)*3.2
=6.8x16.8+16.8x3.2+2.5x3.2
=16.8x(6.8+3.2)+2.5x4x0.8
=16.8x10+10x0.8
=168+8
=176
如果本题有什么不明白可以追问,

72*2.07-1.8*3.6=72*2.07-0.9*7.2=72*2.07-72*0.09=72*(2.07-0.09)=72*1.98=72*(2-0.02)=142.56
6.8*16.8+19.3*3.2=(10-3.2)*16.8+19.3*3.2=168+3.2*(19.3-16.8)=168+3.2*2.5=168+8=176