脱式计算能用简算要简算:(1)19.875-(5.5+8)???????????????(2)[+(6.4-4)×]÷(3)(+)×23×19????????????

发布时间:2020-08-06 15:29:23

脱式计算能用简算要简算:
(1)19.875-(5.5+8)???????????????
(2)[+(6.4-4)×]÷
(3)(+)×23×19???????????????
(4)27.2×+3×12.5%+0.125.

网友回答

解:(1)19.875-(5.5+8),
=19.875-5.5-8,
=19.875-8-5.5,
=19.875-8.875-5.5,
=11-5.5,
=5.5;

(2)[+(6.4-4)×]÷,
=[+(6.4-4.4)×]÷,
=[+2×]÷,
=[+5]×,
=×,
=;

(3)(+)×23×19,
=×23×19+×23×19,
=23+19,
=42;

(4)27.2×+3×12.5%+0.125,
=27.2×0.125+3.8×0.125+0.125,
=(27.2+3.8+1)×0.125,
=32×0.125,
=4.
解析分析:(1)去括号后交换两个减数的位置,可以使计算变得简单;
(2)按四则混合运算的计算法则进行计算;
(3)运用乘法分配律分配简算;
(4)分数、百分数化成小数后运用乘法分配律进行简算.

点评:此题考查整数、分数、小数、百分数四则混合运算,计算同时注意运用定律进行简算.
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