题目内容

脱式计算.
2+
4
5
×(0.6-0.25)
11
8
×
5
9
+
29
8
÷
9
5
8×6.5-148×0.65
15
4
×(
8
3
-
4
5
)+15%
1
8
×[
3
4
÷(
3
5
×
10
9
)]
1
8
×[
3
4
÷(
3
5
×
10
9
)].
分析:(1)先算减法,再算乘法,最后算加法;
(2)根据乘法分配律进行计算;
(3)根据乘法分配律进行计算;
(4)根据乘法分配律进行计算;
(5)先算小括号里面的乘法,再算中括号里面的除法,最后算括号外面的乘法;
(6)先算小括号里面的乘法,再算中括号里面的除法,最后算括号外面的乘法.
解答:解:
(1)2+
4
5
×(0.6-0.25),
=2+
4
5
×0.35,
=2+0.28,
=2.28;

(2)
11
8
×
5
9
+
29
8
÷
9
5

=
11
8
×
5
9
+
29
8
×
5
9

=(
11
8
+
29
8
)×
5
9

=5×
5
9

=
25
9


(3)8×6.5-148×0.65,
=8×6.5-14.8×6.5,
=(8-14.8)×6.5,
=-6.8×6.5,
=-44.2;

(4)
15
4
×(
8
3
-
4
5
)+15%,
=
15
4
×
8
3
-
15
4
×
4
5
+15%,
=10-3+0.15,
=7+0.15,
=7.15;

(5)
1
8
×[
3
4
÷(
3
5
×
10
9
)],
=
1
8
×[
3
4
÷
2
3
],
=
1
8
×
9
8

=
9
64


(6)
1
8
×[
3
4
÷(
3
5
×
10
9
)],
=
1
8
×[
3
4
÷
2
3
],
=
1
8
×
9
8

=
9
64
点评:四则运算,先弄清运算顺序,然后再进一步计算,能简算的要简算.
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