题目内容
(2011?郑州模拟)计算,能简算得写出过程.
(1)7.5×
-2.5×
(2)3.5×
+5.5×80%+0.8
(3)24×[(1
-
)×3]
(4)12-1÷4-
×7
(5)(
+
)÷
-1.5.
(1)7.5×
2 |
5 |
2 |
5 |
(2)3.5×
4 |
5 |
(3)24×[(1
5 |
6 |
2 |
3 |
(4)12-1÷4-
1 |
4 |
(5)(
7 |
2 |
14 |
3 |
49 |
9 |
分析:(1)7.5×
-2.5×
,运用乘法分配律的逆运算简算;
(2)3.5×
+5.5×80%+0.8,先把分数和百分数化为小数,然后利用乘法分配律的逆运算简算;
(3)24×[(1
-
)×3],按运算顺序进行计算,先算小括号里的,再算中括号里的,最后算括号外的;
(4)12-1÷4-
×7,先按运算顺序计算,在利用减法的性质简算;
(5)(
+
)÷
-1.5,按运算顺序进行计算,从左向右依次计算.
2 |
5 |
2 |
5 |
(2)3.5×
4 |
5 |
(3)24×[(1
5 |
6 |
2 |
3 |
(4)12-1÷4-
1 |
4 |
(5)(
7 |
2 |
14 |
3 |
49 |
9 |
解答:解:(1)7.5×
-2.5×
,
=(7.5-2.5)×
,
=5×
,
=2;
(2)3.5×
+5.5×80%+0.8,
=3.5×0.8+5.5×0.8+0.8,
=0.8×(3.5+5.5+1),
=0.8×10,
=8;
(3)24×[(1
-
)×3],
=24×[(1
-
)×3],
=24×[
×3],
=24×
,
=84;
(4)12-1÷4-
×7,
=12-(
+
×7),
=12-(1+7)×
=12-8×
,
=12-2,
=10;
(5)(
+
)÷
-1.5,
=(
+
)×
-1.5,
=
×
-1.5,
=
-1.5,
=1.5-1.5,
=0.
2 |
5 |
2 |
5 |
=(7.5-2.5)×
2 |
5 |
=5×
2 |
5 |
=2;
(2)3.5×
4 |
5 |
=3.5×0.8+5.5×0.8+0.8,
=0.8×(3.5+5.5+1),
=0.8×10,
=8;
(3)24×[(1
5 |
6 |
2 |
3 |
=24×[(1
5 |
6 |
4 |
6 |
=24×[
7 |
6 |
=24×
7 |
2 |
=84;
(4)12-1÷4-
1 |
4 |
=12-(
1 |
4 |
1 |
4 |
=12-(1+7)×
1 |
4 |
=12-8×
1 |
4 |
=12-2,
=10;
(5)(
7 |
2 |
14 |
3 |
49 |
9 |
=(
21 |
6 |
28 |
6 |
9 |
49 |
=
49 |
6 |
9 |
49 |
=
3 |
2 |
=1.5-1.5,
=0.
点评:此题考查学生对分数四则混合运算顺序的掌握情况,以及利用所学定律与性质进行简算的能力.
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