问题 解答题
脱式计算,能简算的要简算.
①0.25×
75
31
+
49
31
×25%
7
10
÷(1-
3
4
×
2
5

③(84%÷3+8.72)×(1-
1
9

④12×(
1
2
-
3
4
答案

①0.25×

75
31
+
49
31
×25%

=

1
4
×
75
31
+
49
31
×
1
4

=

1
4
×(
75
31
+
49
31

=

1
4
×4

=1;

7
10
÷(1-
3
4
×
2
5

=

7
10
÷(1-
3
10

=

7
10
÷
7
10

=1;

③(84%÷3+8.72)×(1-

1
9

=(0.84÷3+8.72)×

8
9

=(0.28+8.72)×

8
9

=9×

8
9

=9;

④12×(

1
2
-
3
4

=12×

1
2
-12×
3
4

=6-9

=-3.

单项选择题
单项选择题