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![](https://rs.olm.vn/images/avt/0.png?1311)
A) 3/7 + 4/9 + 4/7 + 5/9 = ( 4/9+5/9) + ( 3/7 + 4/7) = 1+ 1 = 2
B) 1/5 + 4/11 + 4/5 + 7/11 = ( 4/11 + 7/11) + ( 1/5 + 4/5) = 1+1=2
C) 1/15 + 4/15 + 5/18 + 7/18= ( 1/15+4/15) + (5/18+7/15)= 5/15 + 12/15 = 17/15
D) 1/8 + 1/12 + 3/8 + 5/12 = (1/8 + 3/8) + ( 1/12 + 1/12) = 4/8 + 2/12 = 64/96
K nha
![](https://rs.olm.vn/images/avt/0.png?1311)
A) 1/4 + 5/6=6/24+20/24=26/24
B) 2/9 + 1/9 = 3/9
C)1/6 + 3/8 = 8/48 + 18/48 = 26/48
(d) 3/10 + 5/8= 14/80 + 50/80= 64/160
(E) 7/12 + 1/8 = 56/96+12/96=68/192
(G) 3/20 + 7/2=6/24+20/24=26/24
K nha
![](https://rs.olm.vn/images/avt/0.png?1311)
`4/7+4`
`=4/7+4/1`
`=4/7+28/7`
`=32/7`
__
`3+6/11`
`=33/11+6/11`
`=39/11`
__
`3-5/7`
`=3/1-5/7`
`=21/7-5/7`
`=16/7`
__
`21/9-2`
`=21/9-18/9`
`=3/9`
`=1/3`
__
`15/24+2`
`=15/24+48/24`
`=63/24`
`=21/16`
__
`63/45-20/25`
`=63/45-4/5`
`=63/45-36/45`
`=27/45`
`=9/15`
__
`3/4-2/8`
`=3/4-1/4`
`=2/4`
__
`6/7-5/8`
`=48/56-35/56`
`=13/56`
__
`37/45-5/9`
`=37/45-25/45`
`=12/45`
`=4/15`
__
`46/39-11/13`
`=46/39-33/39`
`=13/39`
`=1/2`
__
`5/12+3/4+1/3`
`=5/12+9/12+4/12`
`=14/12+4/12`
`=18/12`
`=3/2`
__
`1/2+3/7+11/14`
`=7/14+6/14+11/14`
`=13/14+11/14`
`=24/14`
`=12/7`
__
`7/10-(1/5+1/4)`
`=7/10-(4/20+5/20)`
`=7/10-9/20`
`=14/20-9/20`
`=5/20`
`=1/4`
__
`15/4-2/3-3/4`
`=(15/4-3/4)-2/3`
`=12/4-2/3`
`=3-2/3`
`=9/3-2/3`
`=7/3`
![](https://rs.olm.vn/images/avt/0.png?1311)
b)1/2*2/3*3/4*4/5*5/6*6/7*7/8*8/9*9/10
=1x2x3x4x5x6x7x8x9
2x3x4x5x6x7x8x9x10
= 1
10
![](https://rs.olm.vn/images/avt/0.png?1311)
a) \(\frac{3}{16}+\frac{4}{15}+\frac{5}{16}+\frac{1}{15}\)
\(=\left(\frac{3}{16}+\frac{5}{16}\right)+\left(\frac{4}{15}+\frac{1}{15}\right)\)
\(=\frac{1}{2}+\frac{1}{3}\)
\(=\frac{5}{6}\)
b) \(\frac{6}{7}\times\frac{8}{15}\times\frac{7}{6}\times\frac{15}{16}\)
\(=\left(\frac{6}{7}\times\frac{7}{6}\right)\times\left(\frac{8}{15}\times\frac{15}{16}\right)\)
\(=1\times\frac{1}{2}=\frac{1}{2}\)
c) \(\frac{19}{20}\times\frac{13}{21}+\frac{9}{20}\times\frac{8}{21}\)
\(=\frac{19\times13}{20\times21}+\frac{9\times8}{20\times21}\)
\(=\frac{247}{420}+\frac{72}{420}\)
\(=\frac{319}{420}\)
![](https://rs.olm.vn/images/avt/0.png?1311)
\(\frac{2}{7}+\frac{5}{7}=\frac{7}{7}=1\)
\(\frac{8}{15}+\frac{6}{15}=\frac{14}{15}\)
\(\frac{2}{3}+\frac{3}{9}+\frac{4}{9}=\frac{6}{9}+\frac{3}{9}+\frac{4}{9}=\frac{9}{9}+\frac{4}{9}=\frac{13}{9}\)
A) 1/7 + 2/7 + 3/7 = 3/7 + 3/7 = 6/7
B) 1/20 + 3/20 + 7/20 = 4/20 + 7/20= 11/20
C) 2/15 + 4/15 + 4/15 = 6/15 + 4/15 = 10/15
D) 1/9 + 7/9 + 4/9= 8/9 + 4/9 = 12/9
K nha
a) \(\frac{1}{7}+\frac{2}{7}+\frac{3}{7}=\frac{1+2+3}{7}=\frac{6}{7}\text{ }\)
b) \(\frac{1}{20}+\frac{3}{20}+\frac{7}{20}=\frac{1+3+7}{20}=\frac{11}{20}\)
c) \(\frac{2}{15}+\frac{4}{15}+\frac{4}{15}=\frac{2+4+4}{15}=\frac{10}{15}=\frac{2}{3}\)
d) \(\frac{1}{9}+\frac{7}{9}+\frac{4}{9}=\frac{1+7+4}{9}=\frac{12}{9}=\frac{4}{3}\)