题目内容
仔细计算.
①(1-
×
)÷
②35×
+1.25
③
×9+7÷
④
÷[1÷(
-
)]
⑤7.77-
+3.33-
⑥下题等号两边相等的,计算结果是一个大于0而小于4的自然数,题中的小数分数各是几?
× (填一个小数)=0.2÷
,
⑦将
,0.5,1.2,
,20这五个数通过添加运算符号(也可以加括号),使计算结果最大,并算出最大值.
①(1-
1 |
6 |
2 |
5 |
7 |
9 |
②35×
4 |
5 |
③
7 |
16 |
16 |
7 |
④
5 |
7 |
2 |
3 |
1 |
5 |
⑤7.77-
5 |
11 |
6 |
11 |
⑥下题等号两边相等的,计算结果是一个大于0而小于4的自然数,题中的小数分数各是几?
5 |
4 |
( ) |
( ) |
⑦将
1 |
6 |
1 |
5 |
分析:(1)(2)(4)根据四则运算的计算顺序进行计算;
(3)先把除法转化为乘法,再根据乘法分配律进行计算;
(5)根据加法交换律和减法的性质进行计算;
(6)可把0.2除以分数转化为乘以分数,再根据乘法交换律解答;
(7)要使结果最大,要根据数据、运算符号及四则混合运算的顺序三者结合起来进行解答.
(3)先把除法转化为乘法,再根据乘法分配律进行计算;
(5)根据加法交换律和减法的性质进行计算;
(6)可把0.2除以分数转化为乘以分数,再根据乘法交换律解答;
(7)要使结果最大,要根据数据、运算符号及四则混合运算的顺序三者结合起来进行解答.
解答:解:(1)(1-
×
)÷
,
=(1-
)÷
,
=
×
,
=
;
(2)35×
+1.25,
=28+1.25,
=29.25;
(3)
×9+7÷
,
=
×9+7×
,
=
×(9+7),
=
×16,
=7;
(4)
÷[1÷(
-
)],
=
÷[1÷
],
=
÷
,
=
;
(5)7.77-
+3.33-
,
=7.77+3.33-
-
,
=(7.77+3.33)-(
+
),
=11.1-1,
=10.1;
(6)
×0.2=0.2÷
,
故答案为:0.2,
.
(7)(
+0.5+1.2÷
)×20,
=(
+0.5+6)×20,
=6
×20,
=
.
1 |
6 |
2 |
5 |
7 |
9 |
=(1-
1 |
15 |
7 |
9 |
=
14 |
15 |
9 |
7 |
=
6 |
5 |
(2)35×
4 |
5 |
=28+1.25,
=29.25;
(3)
7 |
16 |
16 |
7 |
=
7 |
16 |
7 |
16 |
=
7 |
16 |
=
7 |
16 |
=7;
(4)
5 |
7 |
2 |
3 |
1 |
5 |
=
5 |
7 |
7 |
15 |
=
5 |
7 |
15 |
7 |
=
1 |
3 |
(5)7.77-
5 |
11 |
6 |
11 |
=7.77+3.33-
5 |
11 |
6 |
11 |
=(7.77+3.33)-(
5 |
11 |
6 |
11 |
=11.1-1,
=10.1;
(6)
5 |
4 |
4 |
5 |
故答案为:0.2,
4 |
5 |
(7)(
1 |
6 |
1 |
5 |
=(
1 |
6 |
=6
2 |
3 |
=
400 |
3 |
点评:本题主要考查了学生四则运算的计算能力,以及在计算中灵活运用简便算法的计算能力.
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