题目内容
(2010?龙湾区)用递等式计算,怎样简便就怎样算
(1)3.7-2.2+7.3-7.8
(2)375+450÷18×25
(3)2.9×
+1.1×
(4)
÷(
-
)
(1)3.7-2.2+7.3-7.8
(2)375+450÷18×25
(3)2.9×
1 |
8 |
1 |
8 |
(4)
1 |
4 |
3 |
4 |
1 |
2 |
分析:(1)运用加法结合律和减法的性质简算;
(2)先算除法,再算乘法,最后算加法;
(3)运用乘法分配律简算;
(4)先算小括号里面的减法,再算括号外的除法.
(2)先算除法,再算乘法,最后算加法;
(3)运用乘法分配律简算;
(4)先算小括号里面的减法,再算括号外的除法.
解答:解:(1)3.7-2.2+7.3-7.8,
=(3.7+7.3)-(2.2+7.8),
=11-10,
=1;
(2)375+450÷18×25
=375+25×25
=375+625
=1000;
(3)2.9×
+1.1×
,
=(2.9+1.1)×
,
=4×
,
=
;
(4)
÷(
-
),
=
÷
,
=1.
=(3.7+7.3)-(2.2+7.8),
=11-10,
=1;
(2)375+450÷18×25
=375+25×25
=375+625
=1000;
(3)2.9×
1 |
8 |
1 |
8 |
=(2.9+1.1)×
1 |
8 |
=4×
1 |
8 |
=
1 |
2 |
(4)
1 |
4 |
3 |
4 |
1 |
2 |
=
1 |
4 |
1 |
4 |
=1.
点评:本题考查了四则混合运算,注意运算顺序和运算法则,灵活运用所学的运算定律进行简便计算.
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