分析:(1)、(2)、(3)、(4)、(5)、(6)是帶分數的加減法,整數部分和分數部分分開進行加減;
(7)、(12)把分數化成小數再計算;
(8)、(9)、(10)、(12)把小數化成分數再計算;
(11)去掉括號后在計算.
解答:解:(1)2
+1
,
=(2+1)+(
+
),
=3+
,
=3
;
(2)9
-5
,
=(9-5)+(
-
),
=4+
,
=4
;
(3)6-4
,
=5+1-4
,
=(5-4)+(1-
),
=1+
,
=1
;
(4)4
-3,
=(4-3)+
,
=1+
,
=1
;
(5)9
-3
,
=8
-3
,
=(8-3)+(
-
),
=5+
,
=5
;
(6)4
-2
,
=3
-2
,
=(3-2)+(
-
),
=1+
,
=1
;
(7)1
-0.45+
,
=1.75-0.45+0.4,
=1.3+0.4,
=1.7;
(8)3
+4.25-
,
=3
+4
-
,
=(3+4)+(
+
-
),
=7+
,
=7
;
(9)2
+3.75-1
,
=2
+3
-1
,
=(2+3-1)+(
+
-
),
=4+
,
=4
;
(10)6.875+(4.5-1
),
=6
+4
-1
,
=(6+4-1)+(
+
-
),
=9+
,
=9
;
(11)6.94-(4.94+1
),
=6.94-4.94-1
,
=2-1
,
=2-1-
,
=1-
,
=
;
(12)4
-1
-0.2,
=4.9-1.8-0.2,
=3.1-0.2,
=2.9.
點評:帶分數的加減法,整數部分加減整數部分,分數部分加減分數部分,分數部分不夠減的,從整數部分拿出一個1來化成假分數,再進行加減,是小數的,先化成分數,再進行計算.