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654398 + 362 + 999 + 51
= ( 654398 + 362 ) + ( 999 + 51 )
= 654760 + 1050
= 655810
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A. = 14/15 * 15/23 * 23/21
= 14/23 * 23/21
= 14/21
B. = 1/2 * (9/10 + 8/10 - 7/10)
= 1/2 * 10/10
= 1/2 * 1
= 1/2
a) \(\frac{14}{15}\cdot\frac{23}{21}\cdot\frac{15}{23}=\frac{14}{21}=\frac{2}{3}\)
b)\(\frac{1}{2}\cdot\frac{9}{10}+\frac{1}{2}\cdot\frac{8}{10}-\frac{1}{2}\cdot\frac{7}{10}=\frac{1}{2}\cdot\left(\frac{9}{10}+\frac{8}{10}-\frac{7}{10}\right)=\frac{1}{2}\cdot1=\frac{1}{2}\)
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a, 6257+989+743
=(6257+743)+989
=7000+989
=7989
b, 5798+322+4678
=(4678+322)+5798
=5000+5798
=10798
a,6257+989+743=(6257+743)+989=7000+989=7989
b,5798+322+4678=5798+(322+4678)=5798+5000=10798
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a) 6257 + 989 + 743
= 6257 +743 + 989
= 7000 + 989 = 7989
b) 5798 + 322 + 4678
= 5798 + 5000 = 10798
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\(25\times32\times125\times15\\=(25\times4)\times(8\times125)\times15\\=100\times1000\times15\\=100000\times15\\=1500000\)
25 x 32 x 125 x 15
=(125 x 32 ) x (25 x 15 )
= 4000 x 375
=1 500 000
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a,2009x867+2009x133=2009x(867+133)=2009x1000=2009000
b,có vẻ sai đề.