题目内容
(1)
|
(2)
|
(3)1.8÷2.7-17÷51 | ||||||||||||||
(4)99.9×99+99.9 | (5)15.8-
|
(6)3×9×(
|
分析:(1)据四则混合运算的计算顺序计算即可:先算乘除,再算加减,有括号的打先算括号里面的;
(2)(4)(6)可根据乘法分配律进行简便计算;
(3)可将式中的除法算式化为分数进行计算;
(5)可据加法交换律、结合律及一个数减两个数等于减去这两个数的和的减法性质进行简便计算.
(2)(4)(6)可根据乘法分配律进行简便计算;
(3)可将式中的除法算式化为分数进行计算;
(5)可据加法交换律、结合律及一个数减两个数等于减去这两个数的和的减法性质进行简便计算.
解答:解:(1)
×[
+(
-0.25)],
=
×[
+(
-
)],
=
×[
+
],
=
×
,
=
;
(2)
×
+
÷
,
=
×
+
×
,
=(
+
)×
,
=1×
,
=
;
(3)1.8÷2.7-17÷51,
=
-
,
=
;
(4)99.9×99+99.9,
=(99+1)×99.9,
=100×99.9,
=9990;
(5)15.8-
+14.2-
,
=(15.8+14.2)-(
+
),
=30-1,
=29;
(6)3×9×(
+
)
=27×
+27×
,
=9+3,
=12.
8 |
9 |
3 |
4 |
7 |
16 |
=
8 |
9 |
3 |
4 |
7 |
16 |
1 |
4 |
=
8 |
9 |
3 |
4 |
3 |
16 |
=
8 |
9 |
15 |
16 |
=
5 |
6 |
(2)
9 |
20 |
11 |
25 |
14 |
25 |
20 |
9 |
=
9 |
20 |
11 |
25 |
14 |
25 |
9 |
20 |
=(
11 |
25 |
14 |
25 |
9 |
20 |
=1×
9 |
20 |
=
9 |
20 |
(3)1.8÷2.7-17÷51,
=
2 |
3 |
1 |
3 |
=
1 |
3 |
(4)99.9×99+99.9,
=(99+1)×99.9,
=100×99.9,
=9990;
(5)15.8-
7 |
18 |
11 |
18 |
=(15.8+14.2)-(
7 |
18 |
11 |
18 |
=30-1,
=29;
(6)3×9×(
1 |
3 |
1 |
9 |
=27×
1 |
3 |
1 |
9 |
=9+3,
=12.
点评:在除法算式的计算中,如果式中的数不能被除尽,可将式中的除法算式化为分数进行计算.

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