题目内容
脱式计算.(能简便的要简便) (1)2005-395+605 | (2)16×125×21 | (3)![]() ![]() |
(4)![]() ![]() | (5)(![]() ![]() ![]() | (6)4.8×96+4.8÷![]() |
解:(1)2005-395+605,
=(2000+5)-(400-5)+(600+5),
=(2000-400+600)+5+5+5,
=2200+15,
=2215;
(2)16×125×21,
=2×8×125×21,
=2×21×(8×125),
=42×1000,
=42000;
(3)
÷(1-
),
=
÷
,
=
,
=
;
(4)
-8×
,
=
-
,
=
,
=
;
(5)(
)÷
,
=(
)÷
,
=
×
,
=
;
(6)4.8×96+4.8÷
,
=4.8×96+4.8×4,
=(96+4)×4.8,
=100×4.8,
=480.
分析:(1)把2005看作(2000+5),395看作(400-5),605看作(600+5),运用凑整法进行简算;
(2)根据数字特点,把16看作2×8,运用乘法乘法交换律和结合律简算;
(3)按运算顺序进行计算,先算括号内的,再算括号外的;
(4)先算乘法,再算减法;
(5)先算括号内的,再算括号外的;
(6)先把除法改为乘法,然后用乘法分配律的逆运算简算.
点评:在脱式计算中,特别要注意运算顺序以及运算性质、运算定律的正确运用.
=(2000+5)-(400-5)+(600+5),
=(2000-400+600)+5+5+5,
=2200+15,
=2215;
(2)16×125×21,
=2×8×125×21,
=2×21×(8×125),
=42×1000,
=42000;
(3)


=


=

=

(4)


=


=

=

(5)(


=(


=


=

(6)4.8×96+4.8÷

=4.8×96+4.8×4,
=(96+4)×4.8,
=100×4.8,
=480.
分析:(1)把2005看作(2000+5),395看作(400-5),605看作(600+5),运用凑整法进行简算;
(2)根据数字特点,把16看作2×8,运用乘法乘法交换律和结合律简算;
(3)按运算顺序进行计算,先算括号内的,再算括号外的;
(4)先算乘法,再算减法;
(5)先算括号内的,再算括号外的;
(6)先把除法改为乘法,然后用乘法分配律的逆运算简算.
点评:在脱式计算中,特别要注意运算顺序以及运算性质、运算定律的正确运用.

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