题目内容
计算. 2009×
|
24×(
|
(3.12+0.9)÷[(1-0.4)÷0.1] | ||||||||||||||
(4.7+3
|
|
|
分析:算式(1)可将2009变为2010-1后根据乘法分配律计算;
算式(2)可根据乘法分配律计算;
算式(3)(4)根据四则混合运算的运算顺序计算即可:先算乘除,再算加减,有括号的要先算括号里面的;
(5)可根据等式的基本性质进行解方程:方程两边同时加上、减去、乘以或除以同一个数,等式仍然成立;
(6)可根据比例的基本性质:比例的两外项之积等于两内项之积,以及等式的性质进行解比例.
算式(2)可根据乘法分配律计算;
算式(3)(4)根据四则混合运算的运算顺序计算即可:先算乘除,再算加减,有括号的要先算括号里面的;
(5)可根据等式的基本性质进行解方程:方程两边同时加上、减去、乘以或除以同一个数,等式仍然成立;
(6)可根据比例的基本性质:比例的两外项之积等于两内项之积,以及等式的性质进行解比例.
解答:解:(1)2009×
=(2010-1)×
,
=2010×
-
,
=2009-
,
=2008
;
(2)24×(
-
+
)
=24×
-24×
+24×
,
=20-6+16,
=30;
(3)(3.12+0.9)÷[(1-0.4)÷0.1]
=4.02÷[0.6÷0.1],
=4.02÷6,
=0.67;
(4)(4.7+3
)÷[(4
-3.5)×2
]
=(4.7+3.4)÷[(
-
)×
],
=8.1÷[(
-
)×
],
=8.1÷[
×
],
=8.1×
,
=5.4;
(5)
χ-1=0.9×
x-1=0.6,
x÷
=1.6÷
,
x=2.4;
(6)
:
=8:χ
x=
×8,
x÷
=
×8÷
,
x=48.
2009 |
2010 |
=(2010-1)×
2009 |
2010 |
=2010×
2009 |
2010 |
2009 |
2010 |
=2009-
2009 |
2010 |
=2008
1 |
2010 |
(2)24×(
5 |
6 |
1 |
4 |
2 |
3 |
=24×
5 |
6 |
1 |
4 |
2 |
3 |
=20-6+16,
=30;
(3)(3.12+0.9)÷[(1-0.4)÷0.1]
=4.02÷[0.6÷0.1],
=4.02÷6,
=0.67;
(4)(4.7+3
2 |
5 |
1 |
7 |
1 |
3 |
=(4.7+3.4)÷[(
29 |
7 |
7 |
2 |
7 |
3 |
=8.1÷[(
58 |
14 |
49 |
14 |
7 |
3 |
=8.1÷[
9 |
14 |
7 |
3 |
=8.1×
2 |
3 |
=5.4;
(5)
2 |
3 |
2 |
3 |
2 |
3 |
2 |
3 |
2 |
3 |
2 |
3 |
x=2.4;
(6)
1 |
9 |
2 |
3 |
1 |
9 |
2 |
3 |
1 |
9 |
1 |
9 |
2 |
3 |
1 |
9 |
x=48.
点评:在解比例与解方程时要注意等号的对齐.
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