题目内容
脱式计算(能简算的要简算).
(1)
×18+12÷
(2)
-
÷
-
(3)99.5×27.5+0.5×27.5
(4)
×[(
-
)÷
].
解:(1)
×18+12÷
,
=15+12×6,
=15+72,
=87;
(2)
-
÷
-
,
=
-
×
-
,
=
-
-
,
=
-(
+
),
=
-1,
=
;
(3)99.5×27.5+0.5×27.5,
=(99.5+0.5)×27.5,
=100×27.5,
=2750;
(4)
×[(
-
)÷
],
=
×[
×
],
=
×
,
=
.
分析:(1)把除法改为乘法,通过约分计算即可;
(2)先算除法,原式变为
-
-
,再运用减法的性质简算;
(3)运用乘法分配律简算;
(4)先算小括号内的,再算中括号内的,最后算括号外的.
点评: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.


=15+12×6,
=15+72,
=87;
(2)




=




=



=



=

=

(3)99.5×27.5+0.5×27.5,
=(99.5+0.5)×27.5,
=100×27.5,
=2750;
(4)




=



=


=

分析:(1)把除法改为乘法,通过约分计算即可;
(2)先算除法,原式变为



(3)运用乘法分配律简算;
(4)先算小括号内的,再算中括号内的,最后算括号外的.
点评: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.

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