【题目】
(2012?民乐县模拟)脱式计算,能简算的要简算
9.81×0.1+0.5×98.1+0.049×981
2
14÷[(2
13-1.2)×
34+0.05]
100-32×0.125×0.25
[1-(
12-
14)]×
23.
分析:(1)先根据积不变规律,把9.81×0.1变成98.1×0.01,0.049×981变成0.49×98.1,再根据乘法分配律简算;
(2)先算小括号里面的减法,再算中括号里面的乘法,然后算中括号里面的加法,最后算括号外的除法;
(3)先把32分解成4×8,再运用乘法结合律简算,最后算减法;
(4)先算小括号里面的减法,再算中括号里面的减法,最后算括号外的乘法.解答:解:(1)9.81×0.1+0.5×98.1+0.049×981,
=98.1×0.01+0.5×98.1+0.49×98.1,
=98.1×(0.01+0.5+0.49),
=98.1×(0.51+0.49),
=98.1×1,
=98.1;
(2)214÷[(213-1.2)×34+0.05],
=214÷[1715×34+0.05],
=214÷[1720+120],
=94÷910,
=52;
(3)100-32×0.125×0.25,
=100-4×8×0.125×0.25,
-100-(4×0.25)×(8×0.125),
=100-1×1,
=100-1,
=99;
(4)[1-(12-14)]×23,
=[1-14]×23,
=34×23,
=12.点评:本题考查了运算定律与简便运算,四则混合运算.注意运算顺序和运算法则,灵活运用所学的运算律简便计算.