试题

题目:
计算:
(1)0-(+8)+(-2.7)-(+5);
(2)-3.92+6.24-8.56+4.28;
(3)0.25+
1
12
+(-
2
3
)-
1
4
-
5
12

(4)-
5
6
-3.74-(-3.74)+
5
6
+17.8

答案
解:(1)原式=0-8-2.7-5,
=-15.7;

(2)原式=(6.24+4.28)-(3.92+8.56),
=10.52-12.48,
=-1.96;

(3)原式=(
1
4
-
1
4
)+(
1
12
-
5
12
-
2
3
),
=-1;

(4)原式=(-
5
6
+
5
6
)+(-3.74+3.74)+17.8,
=17.8.
解:(1)原式=0-8-2.7-5,
=-15.7;

(2)原式=(6.24+4.28)-(3.92+8.56),
=10.52-12.48,
=-1.96;

(3)原式=(
1
4
-
1
4
)+(
1
12
-
5
12
-
2
3
),
=-1;

(4)原式=(-
5
6
+
5
6
)+(-3.74+3.74)+17.8,
=17.8.
考点梳理
有理数的加减混合运算.
(1)(2)将同号的数先相加,再把异号的数相加;(3)将小数化为分数,把同分母先相加;(4)把相反数抵消即可.
本题考查了有理数的加减混合运算,关键是运用加法的运算律,结合律使运算简便.
计算题.
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