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用简便方法计算下面各题8.7×0.72+0.28×8.7+8.3.9×9.9+3.91.25×88574.64×21250×0.037+0.125×160+12.5×2.7347×69+653×31+306×19.

题目详情
用简便方法计算下面各题
8.7×0.72+0.28×8.7+8.
3.9×9.9+3.9
1.25×88
574.64×2
1250×0.037+0.125×160+12.5×2.7
347×69+653×31+306×19.
▼优质解答
答案和解析
(1)8.7×0.72+0.28×8.7+8
=8.7×(0.72+0.28)+8
=8.7×1+8
=8.7+8
=16.7;

(2)3.9×9.9+3.9
=3.9×(9.9+1)
=3.9×10.9
=42.51;

(3)1.25×88
=1.25×(8×11)
=(1.25×8)×11
=10×11
=110;

(4)574.64×2=1149.28;

(5)1250×0.037+0.125×160+12.5×2.7
=125×0.37+125×0.160+125×0.27
=125×(0.37+0.16+0.27)
=125×0.8
=100;

(6)347×69+653×31+306×19
=347×(31+38)+653×31+306×19
=347×31+347×38+653×31+306×19
=347×31+653×31+347×2×19+306×19
=(347+653)×31+694×19+306×19
=(347+653)×31+(694+306)×19
=1000×31+1000×19
=1000×(31+19)
=1000×50
=50000.