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a) 45,5 x 21 + 54,5 x 21
= 21 x (45,5 + 54,5)
= 21 x 100
= 2100
b) 145,5 x 5,09 - 33,5 x 5,09 - 12 x 5,09
= 5,09 x (145,5 - 33,5 - 12)
= 5,09 x 100
= 509
a)45,5x21+54,5x21
=21x(45,5+54,5)
=21x100
=2100
b)154,5 x 5,09 - 33,5 x 5,09 -12 x 5,09
=5,09 x(154,5 - 33,5 - 12)
=5,09 x 100
=509
![](https://rs.olm.vn/images/avt/0.png?1311)
#Trl :
\(145,5\times5,09-5,09\times33,5-12\times5,09\)
\(=5,09\times\left(145,5-33,5-12\right)\)
\(=5,09\times100\)
\(=509\)
![](https://rs.olm.vn/images/avt/0.png?1311)
![](https://rs.olm.vn/images/avt/0.png?1311)
\(145,5\cdot5,09-33,5\cdot5,09-12\cdot5,09\)
\(=5,09\cdot\left(145,5-33,5-12\right)\)
\(=5,09\cdot100\)
\(=509\)
145,5*5,09-33,5*5,09-12*5,09
=5,09*(145,5-33,5-12)
=5,09*100
=509
![](https://rs.olm.vn/images/avt/0.png?1311)
![](https://rs.olm.vn/images/avt/0.png?1311)
\(\text{b.( 4,91+12,57)+( 5,09+7,43)}\)
\(=4,91+12,57+5,09+7,43\)
\(=\left(4,91+5,09\right)+\left(12,57+7,43\right)\)
\(=10+20\)
\(=30\)
học tốt
45,5 x 21 + 54,5 x 21 = ( 45,5+54,5)x 21 = 100x21=2100
45,5 * 21+54,5 *21=(45,5+54,5)*21=100*21=2100
145,5*5,09-33,5*5,09-12*5,09=(145,5-33,5-12)*5,09=100*5,09=509