题目内容
脱式计算
(21+
|
3-
|
8×
|
解方程:50%x-
|
分析:(1)运用乘法分配律简算;
(2)先算乘法,再算减法;
(3)先算乘除,再算加法;
(4)原式变为(50%-
)x=10,即0.25x=10,根据等式的性质,两边同除以0.25即可.
(2)先算乘法,再算减法;
(3)先算乘除,再算加法;
(4)原式变为(50%-
1 |
4 |
解答:解:(1)(21+
)×
,
=21×
+
×
,
=15+
,
=15
;
(2)3-
×
-
,
=3-
-
,
=3-(
+
),
=3-
,
=2
;
(3)8×
+
÷4,
=8×
+
×
,
=
+
,
=
;
(4)50%x-
x=10,
(50%-
)x=10,
(0.5-0.25)x=10,
0.25x=10,
0.25x÷0.25=10÷0.25,
x=40.
2 |
5 |
5 |
7 |
=21×
5 |
7 |
2 |
5 |
5 |
7 |
=15+
2 |
7 |
=15
2 |
7 |
(2)3-
2 |
3 |
10 |
21 |
2 |
7 |
=3-
20 |
63 |
18 |
63 |
=3-(
20 |
63 |
18 |
63 |
=3-
38 |
63 |
=2
25 |
63 |
(3)8×
5 |
6 |
2 |
5 |
=8×
5 |
6 |
2 |
5 |
1 |
4 |
=
20 |
3 |
1 |
10 |
=
203 |
30 |
(4)50%x-
1 |
4 |
(50%-
1 |
4 |
(0.5-0.25)x=10,
0.25x=10,
0.25x÷0.25=10÷0.25,
x=40.
点评:考查了运算定律与简便运算,四则混合运算.注意运算顺序和运算法则,灵活运用所学的运算律简便计算;同时考查了根据等式的性质解方程.
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