直接寫得數(shù)
3
4
+
1
2
=

1
6
÷7=

13
14
×
2
13
=

1
4
÷
1
2
=
1
12
×8=
3
4
=
15×
4
5
=
1
3
-
1
4
=
4
5
÷
2
5
=
4
9
×
3
4
=
3
4
×
6
7
=
7
5
÷
5
7
=
分析:分?jǐn)?shù)加減法:要注意先通分成同分母分?jǐn)?shù),再分母不變,分子相加減;
分?jǐn)?shù)乘法:分子和分母先約分,再計(jì)算;
分?jǐn)?shù)除法:先改寫成乘除數(shù)的倒數(shù),再按照分?jǐn)?shù)乘法的法則進(jìn)行計(jì)算.
解答:

解:
3
4
+
1
2
=
5
4

1
6
÷7=
1
42
,

13
14
×
2
13
=
1
7
,

1
4
÷
1
2
=
1
2
1
12
×8=
2
3
,
3
4
=12,
15×
4
5
=12,
1
3
-
1
4
=
1
12
,
4
5
÷
2
5
=2,
4
9
×
3
4
=
1
3
,
3
4
×
6
7
=
9
14
,
7
5
÷
5
7
=
49
25
點(diǎn)評(píng):此題考查快速計(jì)算的能力,要注意看清運(yùn)算符號(hào),根據(jù)數(shù)據(jù)的特點(diǎn),用自己喜歡的方法計(jì)算.
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