题目内容
计算(能简算的要简算)
(1)3
×15
-1.25×15
(2)7
+3
+2
+6.1
(3)3-(
÷6
+2
)
(4)9
÷[(38.02+1.98)×0.5].
(1)3
1 |
4 |
2 |
3 |
2 |
3 |
(2)7
5 |
6 |
9 |
10 |
1 |
6 |
(3)3-(
4 |
5 |
2 |
3 |
2 |
5 |
(4)9
9 |
20 |
考点:分数的四则混合运算,分数的简便计算
专题:运算顺序及法则,运算定律及简算
分析:(1)利用乘法分配律简算;
(2)利用加法交换律与结合律简算;
(3)先算除法,再算加法,最后算减法;
(4)先算加法,再算乘法,最后算除法.
(2)利用加法交换律与结合律简算;
(3)先算除法,再算加法,最后算减法;
(4)先算加法,再算乘法,最后算除法.
解答:
解:(1)3
×15
-1.25×15
=
×
-
×
=(
-
)×
=
;
(2)7
+3
+2
+6.1
=(7
+2
)+(6.1+3
)
=10+10
=20;
(3)3-(
÷6
+2
)
=3-(
×
+2
)
=3-(
+2
)
=3-
=
;
(4)9
÷[(38.02+1.98)×0.5]
=
÷[40×0.5]
=
÷20
=
.
1 |
4 |
2 |
3 |
2 |
3 |
=
13 |
4 |
47 |
3 |
5 |
4 |
47 |
3 |
=(
13 |
4 |
5 |
4 |
47 |
3 |
=
94 |
3 |
(2)7
5 |
6 |
9 |
10 |
1 |
6 |
=(7
5 |
6 |
1 |
6 |
9 |
10 |
=10+10
=20;
(3)3-(
4 |
5 |
2 |
3 |
2 |
5 |
=3-(
4 |
5 |
3 |
20 |
2 |
5 |
=3-(
3 |
25 |
2 |
5 |
=3-
63 |
25 |
=
12 |
25 |
(4)9
9 |
20 |
=
189 |
20 |
=
189 |
20 |
=
189 |
400 |
点评:四则混合运算的关键是抓住运算顺序,正确按运算书序计算,适当利用运算定律简算.
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