题目内容
计算:
(1)20
-2.73-8.27+1
(2)
7
+
1
×5
(3)[(88+
)×1.125-54]÷23%
(4)[2
÷(3
-
)×1
]÷4.02.
解:(1)20
-2.73-8.27+1
,
=(20
+1
)-(2.73+8.27),
=21
-11,
=10
;
(2)
7
+
1
×5,
=
7
+
×1
,
=(
+
)×
,
=9×
,
=5;
(3)[(88+
)×1.125-54]÷23%,
=[(88+
)×1
-54]÷23%,
=[(88×
+
×
)-54]÷23%,
=[99+1-54]÷0.23,
=46÷0.23,
=200;
(4)[2
÷(3
-
)×1
]÷4.02,
=[
÷2
×1
]÷4.02,
=[
×
]÷4.02,
=1÷4.02,
=100÷402,
=
.
分析:(1)20
-2.73-8.27+1
,运用加法结合律计算;
(2)
7
+
1
×5,先算
5=
,然后用乘法分配律的逆运算简算;
(3)[(88+
)×1.125-54]÷23%,根据数字特点,把1.125写成分数,然后用乘法分配律简算,由于中括号内的结果是46,所以把23%化为小数计算较简单;
(4)[2
÷(3
-
)×1
]÷4.02,此题注意运算顺序,先算小括号内的,再算中括号内的,最后算括号外的.
点评:此题考查了学生对运算顺序的掌握,以及运用运算定律灵活简算的能力.


=(20


=21

=10

(2)




=




=(



=9×

=5;
(3)[(88+

=[(88+


=[(88×



=[99+1-54]÷0.23,
=46÷0.23,
=200;
(4)[2




=[



=[


=1÷4.02,
=100÷402,
=

分析:(1)20


(2)






(3)[(88+

(4)[2




点评:此题考查了学生对运算顺序的掌握,以及运用运算定律灵活简算的能力.

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