题目内容
递等式计算:(能简便的要简便) 3
|
(
|
9×
| ||||||||||||||||||||
|
2.35+
|
(
| ||||||||||||||||||||
(
|
(
|
25÷(
|
分析:(1)3
×7,把3
看作(3+
),利用乘法分配律比较简便;
(2)(
+1÷
)÷
按运算顺序直接计算就可以了;
(3)9×
×
先约分,再计算;
(4)
×
+
×
,利用乘法分配律比较简便;
(5)2.35+
÷
+2.35按运算顺序计算;
(6)(
+
)÷(
-
),先通分,再计算;
(7)(8)(
+
)÷
、(
+
-
)÷
先转化成乘法,再利用乘法分配律比较简便;
(9)25÷(
-
),先通分,再计算.
1 |
10 |
1 |
10 |
1 |
10 |
(2)(
1 |
2 |
2 |
7 |
15 |
7 |
(3)9×
3 |
8 |
5 |
27 |
(4)
11 |
18 |
5 |
9 |
5 |
9 |
7 |
18 |
(5)2.35+
2 |
9 |
1 |
9 |
(6)(
1 |
4 |
1 |
2 |
2 |
3 |
2 |
5 |
(7)(8)(
3 |
8 |
1 |
4 |
3 |
16 |
3 |
4 |
6 |
6 |
3 |
24 |
1 |
24 |
(9)25÷(
1 |
4 |
1 |
9 |
解答:解:(1)3
×7,
=(3×7)+(
×7),
=21+
,
=21
;
(2)(
+1÷
)÷
,
=(
+1×
)×
,
=(
+
)×
,
=4×
,
=
,
=1
;
(3)9×
×
,
=9×
×
,
=
;
(4)
×
+
×
,
=(
+
)×
,
=1×
,
=
;
(5)2.35+
÷
+2.35,
=2.35+
×
+2.35,
=2.35+2+2.35,
=6.7;
(6)(
+
)÷(
-
),
=
÷
,
=
×
,
=
,
=2
;
(7)(
+
)÷
,
=(
+
)×
,
=
×
+
×
,
=2+
,
=3
;
(8)(
+
-
)÷
,
=
×24+
×24-
×24,
=18+4-3,
=19;
(9)25÷(
-
),
=25÷(
-
),
=25×
,
=180.
1 |
10 |
=(3×7)+(
1 |
10 |
=21+
7 |
10 |
=21
7 |
10 |
(2)(
1 |
2 |
2 |
7 |
15 |
7 |
=(
1 |
2 |
7 |
2 |
7 |
15 |
=(
1 |
2 |
7 |
2 |
7 |
15 |
=4×
7 |
15 |
=
28 |
15 |
=1
13 |
15 |
(3)9×
3 |
8 |
5 |
27 |
=9×
3 |
8 |
5 |
27 |
=
5 |
8 |
(4)
11 |
18 |
5 |
9 |
5 |
9 |
7 |
18 |
=(
11 |
18 |
7 |
18 |
5 |
9 |
=1×
5 |
9 |
=
5 |
9 |
(5)2.35+
2 |
9 |
1 |
9 |
=2.35+
2 |
9 |
9 |
1 |
=2.35+2+2.35,
=6.7;
(6)(
1 |
4 |
1 |
2 |
2 |
3 |
2 |
5 |
=
3 |
4 |
4 |
15 |
=
3 |
4 |
15 |
4 |
=
45 |
16 |
=2
13 |
16 |
(7)(
3 |
8 |
1 |
4 |
3 |
16 |
=(
3 |
8 |
1 |
4 |
16 |
3 |
=
3 |
8 |
16 |
3 |
1 |
4 |
16 |
3 |
=2+
4 |
3 |
=3
1 |
3 |
(8)(
3 |
4 |
1 |
6 |
3 |
24 |
1 |
24 |
=
3 |
4 |
1 |
6 |
3 |
24 |
=18+4-3,
=19;
(9)25÷(
1 |
4 |
1 |
9 |
=25÷(
9 |
36 |
4 |
36 |
=25×
36 |
5 |
=180.
点评:计算这类题目,先要认真观察算式特点,能简算的要简算,不能简算按照混合运算的计算方法进行计算,要灵活处理,分别对待.
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