用简便方法计算(2.9*2.5)*0.4 7.65-(4.58-2.35) 30.5*20.8-305*1.08 (6.4-22.4/14)*0.35

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用简便方法计算(2.9*2.5)*0.4 7.65-(4.58-2.35) 30.5*20.8-305*1.08 (6.4-22.4/14)*0.35
用简便方法计算(2.9*2.5)*0.4 7.65-(4.58-2.35) 30.5*20.8-305*1.08 (6.4-22.4/14)*0.35

用简便方法计算(2.9*2.5)*0.4 7.65-(4.58-2.35) 30.5*20.8-305*1.08 (6.4-22.4/14)*0.35
(2.9*2.5)*0.4
=2.9*(2.5*0.4)
=2.9*1
=2.9
.
7.65-(4.58-2.35)
=7.65-4.58+2.35
=7.65+2.35-4.58
=10 - 4.58
=5.42
.
30.5*20.8-305*1.08
=30.5*20.8-30.5*10.8
=30.5*(20.8-10.8)
=30.5*10
=305
.
(6.4-22.4/14)*0.35
=(6.4 - 11.2/7)*0.35
=(6.4 - 1.6)*0.35
=4.8*0.35
=2.4*0.7
=1.68