题目内容
6.计算下面各题,能简算的要简算7.8×10.1=
7.28+3.2÷2.5=
3.5×3.4+5.5×3.4+3.4=
1.25×34.8×80=
0.75×18÷0.15=
78.5÷4÷2.5=
分析 (1)先把10.1分解成10+0.1,再根据乘法分配律简算;
(2)先算除法,再算加法;
(3)运用乘法分配律简算;
(4)运用乘法交换律简算;
(5)根据乘法交换律简算;
(6)根据除法的性质简算.
解答 解:(1)7.8×10.1
=7.8×(10+0.1)
=7.8×10+7.8×0.1
=78+0.78
=78.78;
(2)7.28+3.2÷2.5
=7.28+1.28
=8.56;
(3)3.5×3.4+5.5×3.4+3.4
=(3.5+5.5+1)×3.4
=10×3.4
=34;
(4)1.25×34.8×80
=1.25×80×34.8
=100×34.8
=3480;
(5)0.75×18÷0.15
=0.75÷0.15×18
=5×18
=90;
(6)78.5÷4÷2.5
=78.5÷(4×2.5)
=78.5÷10
=7.85.
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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