题目内容

脱式计算,能简算的要简算.
0.125×0.25×32
1500-18×120÷25     
3
4
×101-0.75
9
20
÷[
3
2
×(0.4+
4
5
)]
4
5
÷[(
1
3
+
2
5
)×
4
11
].
分析:(1)把32看作4×8,运用乘法交换律与结合律简算;
(2)先算乘除,再算减法;
(3)把分数改为小数0.75,运用乘法分配律简算;
(4)(5)题先算小括号内的,再算中括号内的,最后算括号外的.
解答:解:(1)0.125×0.25×32,
=0.125×0.25×4×8,
=0.125×8×(0.25×4),
=1×1,
=1;

(2)1500-18×120÷25,
=1500-86.4,
=1413.6;

(3)
3
4
×101-0.75,
=0.75×101-0.75,
=(101-1)×0.75,
=100×0.75,
=75;

(4)
9
20
÷[
3
2
×(0.4+
4
5
)],
=
9
20
÷[
3
2
×(
2
5
+
4
5
)],
=
9
20
÷[
3
2
×
6
5
],
=
9
20
÷
9
5

=
9
20
×
5
9

=
1
4


(5)
4
5
÷[(
1
3
+
2
5
)×
4
11
],
=
4
5
÷[
11
15
×
4
11
],
=
4
5
÷
4
15

=
4
5
×
15
4

=3.
点评:此题考查了四则混合运算.注意运算顺序和运算法则,灵活运用所学的运算定律简便计算
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