题目内容
下面各题,能简算的要用简便方法计算.
3.9+0.56+6.1+0.44
50÷2.5+1.8×4.5
6.87×[40÷(3.49-3.09)]
0.8×(12.5+0.125)
3.9+0.56+6.1+0.44
50÷2.5+1.8×4.5
6.87×[40÷(3.49-3.09)]
0.8×(12.5+0.125)
分析:(1)运用加法交换律和加法结合律简算;
(2)同时运算除法和乘法,再算加法;
(3)先算小括号里面的减法,再算中括号里面除法,最后算括号外的乘法;
(4)运用乘法分配律简算.
(2)同时运算除法和乘法,再算加法;
(3)先算小括号里面的减法,再算中括号里面除法,最后算括号外的乘法;
(4)运用乘法分配律简算.
解答:解:(1)3.9+0.56+6.1+0.44,
=(3.9+6.1)+(0.56+0.44),
=10+1,
=11;
(2)50÷2.5+1.8×4.5,
=20+8.1,
=28.1;
(3)6.87×[40÷(3.49-3.09)],
=6.87×[40÷0.4],
=6.87×100,
=687;
(4)0.8×(12.5+0.125),
=0.8×12.5+0.8×0.125,
=10+0.1,
=10.1.
=(3.9+6.1)+(0.56+0.44),
=10+1,
=11;
(2)50÷2.5+1.8×4.5,
=20+8.1,
=28.1;
(3)6.87×[40÷(3.49-3.09)],
=6.87×[40÷0.4],
=6.87×100,
=687;
(4)0.8×(12.5+0.125),
=0.8×12.5+0.8×0.125,
=10+0.1,
=10.1.
点评:此题是考查四则混合运算,要仔细观察算式的特点,灵活运用一些定律进行简便计算.
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