试题

题目:
计算:
(1)4.7-(-8.9)-7.5+(-6)
(2)49
24
25
×(-5)
(3)(
7
9
-2
1
6
-1
3
4
)÷(-
1
6
2
(4)(-5)×3
1
3
+2×3
1
3
-6×3
1
3

(5)(-1)2011-(-22)×(-1)5-36×(-
1
3
)2

答案
解:(1)4.7-(-8.9)-7.5+(-6)
=4.7+8.9-7.5-6
=13.6-13.5
=0.1;

(2)49
24
25
×(-5)
=(50-
1
25
)×(-5)
=50×(-5)-
1
25
×(-5)
=-250+
1
5

=-249
4
5


(3)(
7
9
-2
1
6
-1
3
4
)÷(-
1
6
2
=(
7
9
-2
1
6
-1
3
4
)×36
=28-78-63
=-113;

(4)(-5)×3
1
3
+2×3
1
3
-6×3
1
3

=(-5+2-6)×3
1
3

=-9×3
1
3

=-30;

(5)(-1)2011-(-22)×(-1)5-36×(-
1
3
)2

=-1-4×1-36×
1
9

=-1-4-4
=-9.
解:(1)4.7-(-8.9)-7.5+(-6)
=4.7+8.9-7.5-6
=13.6-13.5
=0.1;

(2)49
24
25
×(-5)
=(50-
1
25
)×(-5)
=50×(-5)-
1
25
×(-5)
=-250+
1
5

=-249
4
5


(3)(
7
9
-2
1
6
-1
3
4
)÷(-
1
6
2
=(
7
9
-2
1
6
-1
3
4
)×36
=28-78-63
=-113;

(4)(-5)×3
1
3
+2×3
1
3
-6×3
1
3

=(-5+2-6)×3
1
3

=-9×3
1
3

=-30;

(5)(-1)2011-(-22)×(-1)5-36×(-
1
3
)2

=-1-4×1-36×
1
9

=-1-4-4
=-9.
考点梳理
有理数的混合运算.
(1)先化简,再按照有理数混合运算的顺序计算即可;
(2)根据乘法分配律简便计算;
(3)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;
(4)根据乘法分配律简便计算;
(5)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.
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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