1樓:█花仔
解:(1)2.15+8.73+1.27+7.85=(2.15+7.85)+(8.73+1.27),=10+10,
=20;
(2)11.87-(8.2+1.87),
=11.87-1.87-8.2,
=10-8.2,
=1.8;
(3)5.42-3.87-1.13,
=5.42-5,
=0.42;
(4)4.38-1.56+0.62-0.44,=(4.38+0.62)-(1.56+0.44),=5-2,
=3; (5)0.4×270×2.5,
=(0.4×2.5)×270,
=270;
(6)(40+1.25)×8,
=40×8+1.25×8,
=320+10,
=330;
(7)(12.5-0.05)×8,
=12.5×8-0.05×8,
=100-0.4,
=99.6;
(8)2.6×8.5+8.5×7.4,
=(2.6+7.4)×8.5,
=85;
(9)9.9×6.9-6.9×3.9,
=(9.9-3.9)×6.9,
=6×6.9,
=41.4;
(10)5.6×99+5.6,
=5.6×(99+1),
=560;
(11)2.5×(1.9+1.9+1.9+1.9),=2.5×4×1.9,
=10×1.9,
=19;
(12)7.2÷1.25÷8,
=7.2÷8÷1.25,
=0.9÷1.25,
=0.72.
下面各題,怎樣簡便就怎樣算. (1)2.15+8.73+1.27+7.85 (2)11.87-(8.2+1.87) (3)5.42-3.87-
2樓:悠悠hanp慎
(1)2.15+8.73+1.27+7.85=(2.15+7.85)+(8.73+1.27),=10+10,
=20;
(2)11.87-(8.2+1.87),
=11.87-1.87-8.2,
=10-8.2,
=1.8;
(3)5.42-3.87-1.13,
=5.42-5,
=0.42;
(4)4.38-1.56+0.62-0.44,=(4.38+0.62)-(1.56+0.44),=5-2,
=3; (5)0.4×270×2.5,
=(0.4×2.5)×270,
=270;
(6)(40+1.25)×8,
=40×8+1.25×8,
=320+10,
=330;
(7)(12.5-0.05)×8,
=12.5×8-0.05×8,
=100-0.4,
=99.6;
(8)2.6×8.5+8.5×7.4,
=(2.6+7.4)×8.5,
=85;
(9)9.9×6.9-6.9×3.9,
=(9.9-3.9)×6.9,
=6×6.9,
=41.4;
(10)5.6×99+5.6,
=5.6×(99+1),
=560;
(11)2.5×(1.9+1.9+1.9+1.9),=2.5×4×1.9,
=10×1.9,
=19;
(12)7.2÷1.25÷8,
=7.2÷8÷1.25,
=0.9÷1.25,
=0.72.
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