题目内容
下面各题,怎样简便就怎样算.
①75÷4+24×
+
;
②98.3-3.32-5.68+10.7;
③
-
×(
-
);
④
÷[(
+20%)×
];
⑤(
+0.2)÷0.25×250%;
⑥(
+
)÷
+
.
①75÷4+24×
1 |
4 |
1 |
4 |
②98.3-3.32-5.68+10.7;
③
3 |
4 |
3 |
4 |
17 |
21 |
2 |
7 |
④
1 |
5 |
2 |
3 |
1 |
13 |
⑤(
3 |
4 |
⑥(
4 |
5 |
1 |
4 |
7 |
3 |
7 |
10 |
考点:整数、分数、小数、百分数四则混合运算,运算定律与简便运算
专题:运算顺序及法则,运算定律及简算
分析:①根据运算顺序先乘、除,再应用加法交换、结合律可使计算简便(可把分数化成小数).
②根据加法交换、结合律,把98.3和10.7结合,3.32和5.68结合(注意运算符号的改变)可使计算简便.
③按照运算顺序计算比较简便,先用乘法分配律计算
×(
-
)反而不简便.
④把20%化成
,按照运算顺序计算即可.
⑤把小数、百分数都化成分数,不规则根据运算顺序计算即可.分成分数的好处是乘时直接约分,若化成小数列竖式计算比较麻烦.
⑥按照运算顺序计算即可.
②根据加法交换、结合律,把98.3和10.7结合,3.32和5.68结合(注意运算符号的改变)可使计算简便.
③按照运算顺序计算比较简便,先用乘法分配律计算
3 |
4 |
17 |
21 |
2 |
7 |
④把20%化成
1 |
5 |
⑤把小数、百分数都化成分数,不规则根据运算顺序计算即可.分成分数的好处是乘时直接约分,若化成小数列竖式计算比较麻烦.
⑥按照运算顺序计算即可.
解答:
解:
①75÷4+24×
+
=18.75+6+0.25
=18.75+0.25+6
=19+6
=25;
②98.3-3.32-5.68+10.7
=(98.3+10.7)-(3.32+5.68)
=109-9
=100;
③
-
×(
-
)
=
-
×
=
-
=
;
④
÷[(
+20%)×
]
=
÷[(
+
)×
]
=
÷[
×
]
=
÷
=
×15
=3;
⑤(
+0.2)÷0.25×250%
=(
+
)÷
×
=
×4×
=9
;
⑥(
+
)÷
+
=
×
+
=
+
=1
.
①75÷4+24×
1 |
4 |
1 |
4 |
=18.75+6+0.25
=18.75+0.25+6
=19+6
=25;
②98.3-3.32-5.68+10.7
=(98.3+10.7)-(3.32+5.68)
=109-9
=100;
③
3 |
4 |
3 |
4 |
17 |
21 |
2 |
7 |
=
3 |
4 |
3 |
4 |
11 |
21 |
=
3 |
4 |
11 |
28 |
=
5 |
14 |
④
1 |
5 |
2 |
3 |
1 |
13 |
=
1 |
5 |
2 |
3 |
1 |
5 |
1 |
13 |
=
1 |
5 |
13 |
15 |
1 |
13 |
=
1 |
5 |
1 |
15 |
=
1 |
5 |
=3;
⑤(
3 |
4 |
=(
3 |
4 |
1 |
5 |
1 |
4 |
5 |
2 |
=
19 |
20 |
5 |
2 |
=9
1 |
2 |
⑥(
4 |
5 |
1 |
4 |
7 |
3 |
7 |
10 |
=
21 |
20 |
3 |
7 |
7 |
10 |
=
9 |
20 |
7 |
10 |
=1
3 |
20 |
点评:此题是考查整数、小数、分数的混合计算,首先看各题能否简算,不能简算的不要硬套,按照运算顺序计算即可,分数、小数、百分数混合时加、减尽量化成小数(在能化成有限小数的情况下),可省去通分的麻烦,乘、除尽量化成分数,可约分,省去列竖式的麻烦.
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