试题

题目:
计算
(1)-20+(-14)-(-18)-13
(2)1-
4
7
+
1
5
-
3
7
+
9
5

(3)2
8
9
×(-36)
(用简便方法计算)     
(4))10+(-2)2×(-5)
(5)(-25)÷
5
4
×
4
5
÷(-16)

(6)(-24)×(
1
6
-
1
4
+
1
2

答案
解:(1)-20+(-14)-(-18)-13
=-20-14+18-13
=-29;

(2)1-
4
7
+
1
5
-
3
7
+
9
5

=1-(
4
7
+
3
7
)+(
1
5
+
9
5

=1-1+2
=2;

(3)2
8
9
×(-36)

=(3-
1
9
)×(-36)
=3×(-36)-
1
9
×(-36)
=-108+4
=-104;
     
(4))10+(-2)2×(-5)
=10+4×(-5)
=10-20
=-10;

(5)(-25)÷
5
4
×
4
5
÷(-16)

=25×
4
5
×
4
5
×
1
16

=1;

(6)(-24)×(
1
6
-
1
4
+
1
2

=-24×
1
6
+24×
1
4
-24×
1
2

=-4+6-12
=-10.
解:(1)-20+(-14)-(-18)-13
=-20-14+18-13
=-29;

(2)1-
4
7
+
1
5
-
3
7
+
9
5

=1-(
4
7
+
3
7
)+(
1
5
+
9
5

=1-1+2
=2;

(3)2
8
9
×(-36)

=(3-
1
9
)×(-36)
=3×(-36)-
1
9
×(-36)
=-108+4
=-104;
     
(4))10+(-2)2×(-5)
=10+4×(-5)
=10-20
=-10;

(5)(-25)÷
5
4
×
4
5
÷(-16)

=25×
4
5
×
4
5
×
1
16

=1;

(6)(-24)×(
1
6
-
1
4
+
1
2

=-24×
1
6
+24×
1
4
-24×
1
2

=-4+6-12
=-10.
考点梳理
有理数的混合运算.
(1)先化简,再计算即可;
(2)先算同分母分数,再相加即可;
(3)(6)运用乘法的分配律计算;
(4)按照有理数混合运算的顺序,先乘方后乘除最后算加减,有括号的先算括号里面的;
(5)将除法变为乘法,再约分计算即可.
本题考查的是有理数的运算能力.注意:
(1)要正确掌握运算顺序,在混合运算中要特别注意运算顺序:先三级,后二级,再一级;有括号的先算括号里面的;同级运算按从左到右的顺序;
(2)去括号法则:--得+,-+得-,++得+,+-得-.
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