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a) \(\dfrac{6}{7}=\dfrac{6\times11}{7\times11}=\dfrac{66}{77}\) ; \(\dfrac{5}{11}=\dfrac{5\times7}{11\times7}=\dfrac{35}{77}\)
b) \(\dfrac{5}{9}=\dfrac{5\times5}{9\times5}=\dfrac{25}{45}\) ; \(\dfrac{9}{5}=\dfrac{9\times9}{5\times9}=\dfrac{81}{45}\)
c) \(\dfrac{3}{8}=\dfrac{3\times3}{8\times3}=\dfrac{9}{24}\) ; \(\dfrac{5}{24}\) giữ nguyên phân số
d) \(\dfrac{6}{5}=\dfrac{6\times6}{5\times6}=\dfrac{36}{30}\) ; \(\dfrac{5}{6}=\dfrac{5\times5}{6\times5}=\dfrac{25}{30}\)
\(#Wendy.Dang\)
a) 6/7 và 5/11
ta có :
6/7=66/77
5/11=35/77
b)5/9 và 9/5
ta có
5/9=25/45
9/5=81/45
C)3/8 và 5/24
ta có :
3/8=9/24
5/24
D)6/5 và 5/6
ta có
6/5=36/30
5/6=25/30
![](https://rs.olm.vn/images/avt/0.png?1311)
\(a.\dfrac{3}{4}=\dfrac{3.9}{4.9}=\dfrac{27}{36}\)
\(\dfrac{5}{9}=\dfrac{5.4}{9.4}=\dfrac{20}{36}\)
\(b.\dfrac{5}{6}=\dfrac{5.3}{6.3}=\dfrac{15}{18}\) giữ nguyên phân số còn lại
c. \(\dfrac{3}{8}=\dfrac{3.3}{8.3}=\dfrac{9}{24}\)
\(\dfrac{7}{12}=\dfrac{7.2}{12.2}=\dfrac{14}{24}\)
d. \(\dfrac{11}{12}=\dfrac{11.4}{12.4}=\dfrac{44}{48}\)
giữ nguyên phân số còn lại.
e. \(\dfrac{9}{50}=\dfrac{9.4}{50.4}=\dfrac{36}{200}\)
giữ nguyên phân số còn lại
\(f.\dfrac{1}{3}=\dfrac{1.3}{15.3}=\dfrac{3}{45}\)
\(\dfrac{2}{15}=\dfrac{2.3}{15.3}=\dfrac{6}{45}\)
giữ nguyên phân số còn lại
![](https://rs.olm.vn/images/avt/0.png?1311)
quy đồng mẫu số các phân số sau:
a,3/4 và 5/9 b,5/6 và 7/18 c,3/8 và 7/12 d,11/12 và 7/48 e,61/200 và 9/50 f,1/3;2/15 và 4/45
![](https://rs.olm.vn/images/avt/0.png?1311)
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
![](https://rs.olm.vn/images/avt/0.png?1311)
`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`
\(a,\)\(\dfrac{2}{5};\dfrac{7}{15}\left(MSC:15\right)\)
\(\dfrac{2}{5}=\dfrac{2\times3}{5\times3}=\dfrac{6}{15}\)
\(b,\dfrac{3}{4};\dfrac{5}{6}\left(MSC:12\right)\)
\(\dfrac{3}{4}=\dfrac{3\times3}{4\times3}=\dfrac{9}{12}\)
\(\dfrac{5}{6}=\dfrac{5\times2}{6\times2}=\dfrac{10}{12}\)
\(c,\dfrac{8}{9};\dfrac{8}{11}\left(MSC:99\right)\)
\(\dfrac{8}{9}=\dfrac{8\times11}{9\times11}=\dfrac{88}{99}\)
\(\dfrac{8}{11}=\dfrac{8\times9}{11\times9}=\dfrac{72}{99}\)
\(d,\dfrac{1}{2};\dfrac{2}{3};\dfrac{3}{5}\left(MSC:30\right)\)
\(\dfrac{1}{2}=\dfrac{1\times15}{2\times15}=\dfrac{15}{30}\)
\(\dfrac{2}{3}=\dfrac{2\times10}{3\times10}=\dfrac{20}{30}\)
\(\dfrac{3}{5}=\dfrac{3\times6}{5\times6}=\dfrac{18}{30}\)
![](https://rs.olm.vn/images/avt/0.png?1311)
![](https://rs.olm.vn/images/avt/0.png?1311)
\(\frac{5}{6}=\frac{20}{24}\); \(\frac{1}{4}=\frac{6}{24}\)
\(\frac{3}{5}=\frac{21}{35}\);\(\frac{3}{7}=\frac{15}{35}\)
\(\frac{9}{8}=\frac{81}{72}\);\(\frac{8}{9}=\frac{64}{72}\)
\(\frac{7}{5}=\frac{77}{55}\);\(\frac{8}{11}=\frac{40}{55}\)
\(\frac{5}{12}=\frac{10}{24}\);\(\frac{3}{8}=\frac{9}{24}\)
\(\frac{17}{10}=\frac{119}{70}\);\(\frac{9}{7}=\frac{90}{70}\)
![](https://rs.olm.vn/images/avt/0.png?1311)
a)12/21 và 3/21
b)12/36 và 15/36
c)63/56 và 48/56
Chúc bạn học tốt
![](https://rs.olm.vn/images/avt/0.png?1311)
a) \(\dfrac{4}{7}và\dfrac{5}{6}\)⇔ \(\dfrac{24}{42}và\dfrac{35}{42}\)
b) \(\dfrac{5}{14}và\dfrac{3}{8}\)⇔ \(\dfrac{20}{56}và\dfrac{21}{56}\)
c) \(\dfrac{9}{10}và\dfrac{7}{5}\)⇔ \(\dfrac{9}{10}và\dfrac{14}{10}\)
d) \(\dfrac{3}{5};\dfrac{5}{6}và\dfrac{7}{30}\)⇔ \(\dfrac{18}{30};\dfrac{25}{30}và\dfrac{7}{30}\)
Mẫu số chung : `15`
`9/5=(9xx3)/(5xx3)=27/15`
`6/3=2=(2xx15)/15 = 30/15`
______________________________
Mẫu số chung : `8`
`45/9 =5 =(5xx8)/8 = 40/8`
`7/8` giữ nguyên
________________________________
Mẫu số chung : `a.c`
`9/a=(9xxac)/(axxac)`
`6/c=(6xxac)/(c xx ac)`
\(\dfrac{9}{5}\) và \(\dfrac{6}{3}\) có MSC: `15`
\(\dfrac{9}{5}=\dfrac{9 \times 3}{5 \times 3}=\dfrac{27}{15}\)
\(\dfrac{6}{3}=\dfrac{6 \times 5}{3 \times 5}=\dfrac{30}{15}\)
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\(\dfrac{45}{9}\) và \(\dfrac{7}{8}\) có MSC: `8`
\(\dfrac{45}{9}=5=\dfrac{5 \times 8}{8}=\dfrac{40}{8}\)
\(\dfrac{7}{8}\) giữ nguyên
___________________________________________
\(\dfrac{74}{8}\) và \(\dfrac{5}{6}\) có MSC: `12`
\(\dfrac{74}{8}=\dfrac{37}{4}=\dfrac{37 \times 3}{4 \times 3}=\dfrac{111}{12}\)
\(\dfrac{5}{6}=\dfrac{5 \times 2}{6 \times 2}=\dfrac{10}{12}\)
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\(\dfrac{9}{a}\) và \(\dfrac{6}{c}\) có MSC: `ac`
\(\dfrac{9}{a}=\dfrac{9 \times c}{a \times c}\)
\(\dfrac{6}{c}=\dfrac{6 \times a}{c \times a}=\dfrac{6 \times a}{a \times c}\)