Bài1 . Tính tuận tiện 0,123×450+1,23×55 0,234×3700+23,4×62×26×9
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![](https://rs.olm.vn/images/avt/0.png?1311)
![](https://rs.olm.vn/images/avt/0.png?1311)
a: Sửa đề:\(4,89\cdot4,5+4,89\cdot4,5+4,89\)
\(=4,89\cdot\left(4,5+4,5+1\right)\)
\(=4,89\cdot10=48,9\)
b: \(0,123\cdot7800+1,23\cdot220\)
\(=1,23\cdot780+1,23\cdot220\)
\(=1,23\left(780+220\right)\)
\(=1,23\cdot1000=1230\)
c: \(0,4\cdot0,45\cdot2,5\)
\(=0,4\cdot2,5\cdot0,45\)
\(=1\cdot0,45=0,45\)
d: \(0,2\cdot5,55\cdot50\)
\(=0,2\cdot50\cdot5,55\)
\(=5,55\cdot10=55,5\)
![](https://rs.olm.vn/images/avt/0.png?1311)
a)\(\frac{{ - 2}}{5} + \frac{3}{7} = \frac{{ - 14}}{{35}} + \frac{{15}}{{35}} = \frac{1}{{35}}\)
b)\(0,123 - 0,234 = - \left( {0,234 - 0,123} \right) = - 0,111.\)
![](https://rs.olm.vn/images/avt/0.png?1311)
\(0,123\) x \(5+0,123:0,25+0,123\)
\(=0,123\) x \(5+0,123\) x \(4+0,123\)
\(=0,123\) x \(\left(5+4+1\right)\)
\(=0,123\) x \(10\)
\(=1,23\)
0,123 x 5 + 0,123 : 0,25 + 0,123
= 0,123 x 5 + 0,123 x 4 + 0,123
= 0,123 x ( 5 + 4 + 1 )
= 0,123 x 10
= 1,23
![](https://rs.olm.vn/images/avt/0.png?1311)
0,123 x 5 + 0,123 x 4 + 0,123
= 0,123 x (5+4+1)
=0,123 x 10
= 1,23
0,123 x 5 + 0,123 x 4 + 0,123
= 0,123 x (5+4+1)
=0,123 x 10
= 1,23
![](https://rs.olm.vn/images/avt/0.png?1311)
a: x*2,3-4,6=2,3
=>x*2,3=6,9
=>x=3
b: =0,123(5+4+1)
=0,123*10
=1,23
a: \(0,123\cdot450+1,23\cdot55\)
\(=1,23\cdot45+1,23\cdot55\)
\(=1,23\left(45+55\right)=1,23\cdot100=123\)
b: \(0,234\cdot3700+23,4\cdot62\cdot26\cdot9\)
\(=23,4\cdot37+23,4\cdot62\cdot26\cdot9\)
\(=23,4\left(37+62\cdot26\cdot9\right)=340353\)