题目内容

(2011?北海模拟)递等式计算(能简便的要简便)
①(
3
8
+
5
6
)÷
1
24
②2.5×13×0.42 ③5.3×12-33.46÷0.35
8
9
÷[(
2
5
+
1
10
)×
3
4
]
⑤9.34-(2.34+0.49)
4
5
+
4
5
×19.
分析:(1)把除法转化为乘法,再根据乘法分配律进行计算;
(2)从左到右依次计算;
(3)先算乘除,再算减法;
(4)先算括号里面的,再算中括号里的,最后算除法;
(5)根据减法的性质进行计算;
(6)根据乘法分配律进行计算.
解答:解:(1)(
3
8
+
5
6
)÷
1
24

=(
3
8
+
5
6
)×24,
=
3
8
×24+
5
6
×24,
=9+20,
=29;

(2)2.5×13×0.42,
=32.5×0.42,
=16.65;

(3)5.3×12-33.46÷0.35,
=63.6-95.6,
=-32;

(4)
8
9
÷[(
2
5
+
1
10
)×
3
4
],
=
8
9
÷[
1
2
×
3
4
],
=
8
9
×
8
3

=
64
27


(5)9.34-(2.34+0.49),
=9.34-2.34-0.49,
=7-0.49,
=6.51;

(6)
4
5
+
4
5
×19,
=
4
5
×(1+19),
=
4
5
×20,
=16.
点评:本题主要考查了学生四则运算的计算能力,注意在计算中灵活运用简便算法的能力.
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