用简便方法计算下面各题.(1)12.5×2.5×3.2(2)5.6÷0.32(3)100.1×23(4) 8 9 - 1 2 + 5 8 + 1 2 (5)1- 5 12 - 7 12 (6) 7 18 -( 5 18 - 8 9 )
(1)12.5×2.5×3.2 =12.5×2.5×(0.4×8), =(12.5×8)×(2.5×0.4), =100×1, =100; (2)5.6÷0.32 =5.6÷(0.8×0.4), =5.6÷0.8÷0.4, =7÷0.4, =17.5; (3)100.1×23 =(100+0.1)×23, =100×23+0.1×23, =2300+2.3, =2302.3; (4)
=(
=
=
(5)1-
=1-(
=1-1, =0; (6)
=
=
=1. |
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