(1)92/3−992/3+9992/3= (2)(3/8+1/6−2/9)×72= (3)4.9×51/2+4.9+31/2×4.9= (4)9999+99992= (5)11×12×13-12×1
题目
答案
(1)
9−99+999,
=(9+999-99)+(
+
-
)
=909+
,
=909
;
(2)
(+−)×72,
=
×72+
×72-
×72,
=27+12-16,
=23;
(3)
4.9×5+4.9+3×4.9,
=4.9×(5.5+1+3.5),
=4.9×10,
=49;
(4)9999+9999
2,
=9999×(1+9999),
=9999×10000,
=99990000;
(5)11×12×13-12×13-260,
=(11-1)×12×13-260,
=10×12×13-260,
=1560-260,
=1300;
(6)101×99×999+999,
=999×(101×99+1),
=999×[(100+1)×99+1];
=999×[100×99+99+1],
=999×[9900+99+1],
=999×10000,
=9990000;
(7)
5×3.8+6.2×5.25,
=5.25×(3.8+6.2),
=5.25×10,
=52.5;
(8)1880×199.9-1999×187.9,
=1880×199.9-199.9×1879,
=(1880-1879)×199.9,
=1×199.9,
=199.9.
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