a:\(\dfrac{1}{4}+\dfrac{1}{5}+\dfrac{1}{2}=\dfrac{5}{20}+\dfrac{4}{20}+\dfrac{10}{20}=\dfrac{19}{20}\)

b:\(\dfrac{3}{7}+\dfrac{5}{8}+\dfrac{1}{4}=\dfrac{24}{56}+\dfrac{35}{56}+\dfrac{14}{56}=\dfrac{73}{56}\)

a. 10/13 + 9/16         
=160/208+117/208
=277/208
7/90 + 123/270
=7/90+41/90
=48/90
=8/15

b. 19/21 - 5/12                 
=76/84-35/84
=41/84
 90/100 - 25/40
=9/10-25/40
=36/40-25/40
=11/40

a. 10/13 + 9/16         
=160/208+117/208
=277/208
7/90 + 123/270
=7/90+41/90
=48/90
=8/15

b. 19/21 - 5/12                 
=76/84-35/84
=41/84
 90/100 - 25/40
=9/10-25/40
=36/40-25/40
=11/40

a) \(\dfrac{10}{13}+\dfrac{9}{16}\)                         \(\dfrac{7}{90}+\dfrac{123}{270}\)

= \(\dfrac{160}{208}+\dfrac{117}{208}\)                   = \(\dfrac{7}{90}+\dfrac{41}{90}\)

= \(\dfrac{277}{208}\)                              = \(\dfrac{8}{15}\)

b) \(\dfrac{19}{21}-\dfrac{5}{12}\)                       \(\dfrac{90}{100}-\dfrac{25}{40}\)

= \(\dfrac{76}{84}-\dfrac{35}{84}\)                      = \(\dfrac{9}{10}-\dfrac{25}{40}\)

= \(\dfrac{41}{84}\)                               = \(\dfrac{36}{40}-\dfrac{25}{40}\)

                                      = \(\dfrac{11}{40}\)

Hok tốt 

a: 7/4=28/16

15/16=15/16

b: 1/8=3/24

2/3=16/24

5/2=60/24

c: 2/7=8/28

9/4=63/28

5/28=5/28

a)\(28/16 và 15/16\)

b)\(3/24; 16/24; 60/24\)

c)\(8/28; 63/28; 5/28\)nhé 

a: 4/3=32/24

5/8=15/24

b: 4/5=36/45

5/9=25/45

c: 4/9=16/36

7/12=21/36

d: 1/2=6/12

2/3=8/12

7/12=7/12

4/3 và 5/8 

\(\dfrac{4}{3}=\dfrac{4x8}{3x8}=\dfrac{32}{24}\)

 \(\dfrac{5}{8}=\dfrac{5x3}{8x3}=\dfrac{15}{24}\)

4/5 và 5/9 

\(\dfrac{4}{5}=\dfrac{4x9}{5x9}=\dfrac{36}{45}\)

\(\dfrac{5}{9}=\dfrac{5x5}{9x5}=\dfrac{25}{45}\)

4/9 và 7/12 

  \(\dfrac{4}{9}=\dfrac{4x12}{9x12}=\dfrac{48}{108}\)

\(\dfrac{7}{12}=\dfrac{7x9}{12x9}=\dfrac{63}{108}\)

1/2 ; 2/3 và 7/12 

\(\dfrac{1}{2}=\dfrac{1x6}{2x6}=\dfrac{6}{12}\)

\(\dfrac{2}{3}=\dfrac{2x4}{3x4}=\dfrac{8}{12}\)

\(\dfrac{7}{12}=\dfrac{7x1}{12x1}=\dfrac{7}{12}\)

ko

a: 4/5=12/15

9/15=9/15

b: 7/8=35/40

4/5=32/40

`MSC:15`

`2/5=(2xx3)/(5xx3)= 6/15`

`7/15` giữ nguyên

__

`MSC : 24`

`3/4=(3xx6)/(4xx6)= 18/24`

`5/6 =(5xx4)/(6xx4)= 20/24`

__ 

`MSC : 99`

`8/9 =(8xx11)/(9xx11)= 88/99`

`8/11=(8xx9)/(11xx9)= 72/99`

__

`MSC:30`

`1/2 =(1xx15)/(2xx15)= 15/30`

`2/3=(2xx10)/(3xx10)=20/30`

`3/5=(3xx6)/(5xx6)= 18/30`

\(a,\)\(\dfrac{2}{5};\dfrac{7}{15}\left(MSC:15\right)\)

\(\dfrac{2}{5}=\dfrac{2\times3}{5\times3}=\dfrac{6}{15}\)

\(b,\dfrac{3}{4};\dfrac{5}{6}\left(MSC:12\right)\)

\(\dfrac{3}{4}=\dfrac{3\times3}{4\times3}=\dfrac{9}{12}\)

\(\dfrac{5}{6}=\dfrac{5\times2}{6\times2}=\dfrac{10}{12}\)

\(c,\dfrac{8}{9};\dfrac{8}{11}\left(MSC:99\right)\)

\(\dfrac{8}{9}=\dfrac{8\times11}{9\times11}=\dfrac{88}{99}\)

\(\dfrac{8}{11}=\dfrac{8\times9}{11\times9}=\dfrac{72}{99}\)

\(d,\dfrac{1}{2};\dfrac{2}{3};\dfrac{3}{5}\left(MSC:30\right)\)

\(\dfrac{1}{2}=\dfrac{1\times15}{2\times15}=\dfrac{15}{30}\)

\(\dfrac{2}{3}=\dfrac{2\times10}{3\times10}=\dfrac{20}{30}\)

\(\dfrac{3}{5}=\dfrac{3\times6}{5\times6}=\dfrac{18}{30}\)

a: 5/6=25/30

9/30=9/30

b: 7/8=49/56

5/7=40/56

c: 2/9=4/18

5/18=5/18

d: 3/10=6/20

1/4=5/20

 5/6=25/30

9/30=9/30 

7/8=49/56

5/7=40/56

 2/9=4/18

5/18=5/18

 3/10=6/20

1/4=5/20

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