题目内容
脱式计算. (1)
|
(2)450-450÷18×15 | (3)3÷2.5+0.45×4.8 | ||||||||||||||||||
(4)
|
(5)(3.8+
|
(6)4
|
分析:本题根据四则混合运算的运算顺序计算即可:先算乘除,再算加减,有括号的要先算括号里面的.
解答:解:(1)
÷(
-0.2)
=
÷(
-
),
=
×
,
=
;
(2)450-450÷18×15
=450-25×15,
=450-375,
=75;
(3)3÷2.5+0.45×4.8
=1.2+2.16,
=3.36;
(4)
×[
-(1
-
)]
=
×[
-(
-
)],
=
×[
-
],
=
×
,
=
;
(5)(3.8+
)-(
+2.4÷2
)
=(3.8+0.5)-(
+
×
),
=4.3-(
+
),
=4.3-(0.6+0.9),
=4.3-1.5,
=2.8;
(6)4
÷[2.5-0.4×(2
-1.05)]
=4.2÷[2.5-0.4×(2.8-1.05)],
=4.2÷[2.5-0.4×1.75],
=4.2÷[2.5-0.7],
=4.2÷1.8,
=
.
13 |
20 |
3 |
4 |
=
13 |
20 |
15 |
20 |
4 |
20 |
=
13 |
20 |
20 |
11 |
=
13 |
11 |
(2)450-450÷18×15
=450-25×15,
=450-375,
=75;
(3)3÷2.5+0.45×4.8
=1.2+2.16,
=3.36;
(4)
8 |
9 |
3 |
4 |
7 |
16 |
7 |
8 |
=
8 |
9 |
3 |
4 |
23 |
16 |
14 |
16 |
=
8 |
9 |
12 |
16 |
9 |
16 |
=
8 |
9 |
3 |
16 |
=
1 |
6 |
(5)(3.8+
1 |
2 |
3 |
5 |
2 |
3 |
=(3.8+0.5)-(
3 |
5 |
12 |
5 |
3 |
8 |
=4.3-(
3 |
5 |
9 |
10 |
=4.3-(0.6+0.9),
=4.3-1.5,
=2.8;
(6)4
1 |
5 |
4 |
5 |
=4.2÷[2.5-0.4×(2.8-1.05)],
=4.2÷[2.5-0.4×1.75],
=4.2÷[2.5-0.7],
=4.2÷1.8,
=
7 |
3 |
点评:当算式中同时含有分数与小数时,要根据式中数据的特点,灵活将他们进行互化后再进行计算.
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