问题 解答题
计算下面各题,能简算的要简算
①31.9×18-8×31.9
②21÷(
1
3
+
2
5
)÷
9
11

③(
2
3
+
2
15
)×45
④(1-
1
100
×70)÷
2
7

⑤12×(
1
4
+
1
6
-
1
3

⑥(
3
8
-0.125)÷0.5.
答案

①31.9×18-8×31.9,

=31.9×(18-8),

=31.9×10,

=319;

②21÷(

1
3
+
2
5
)÷
9
11

=21÷

11
15
÷
9
11

=21×

15
11
×
11
9

=35;

③(

2
3
+
2
15
)×45,

=

2
3
×45+
2
15
×45,

=30+6,

=36;

④(1-

1
100
×70)÷
2
7

=(1-

7
10
)÷
2
7

=

3
10
×
7
2

=

21
20

⑤12×(

1
4
+
1
6
-
1
3
),

=12×

1
4
+12×
1
6
-12×
1
3

=3+2-4,

=1;

⑥(

3
8
-0.125)÷0.5,

=(0.375-0.125)÷0.5,

=0.25÷0.5,

=0.5.

单项选择题
单项选择题