如题所述
4.2*(12.5+2.5)×0.7
=4.2*15×0.7
=4.2×0.7*15
=2.94×15
=（3-0.06）×15
=45-0.9
=44.1追问
=4.2*15×0.7
=4.2×0.7*15
=2.94×15
=（3-0.06）×15
=45-0.9
=44.1追问
这不简便
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第1个回答 2018-01-05
4.2*(12.5+2.5)×0.7
=2.1x0.7x2x15
=1.47x30
=44.1追问
=2.1x0.7x2x15
=1.47x30
=44.1追问
为什么怎么做
第2个回答 2018-01-05
4.2×(12.5+2.5)×0.7
=4.2×15×0.7
=（0.6×15）×（7×0.7）
=9×4.9
=10×4.9-1×4.9
=49-4.9
=44.1
=4.2×15×0.7
=（0.6×15）×（7×0.7）
=9×4.9
=10×4.9-1×4.9
=49-4.9
=44.1
第3个回答 2018-01-05
4.2*(12.5+2.5)×0.7
4.2*15*0.7
63*0.7
44.1
4.2*15*0.7
63*0.7
44.1
