giup voi a minh dang can gap ai nhanh minh cho dung nhe

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)\(3\frac{2}{5}.2\frac{1}{7}=\frac{17}{5}.\frac{15}{7}=\frac{51}{7}\)

b) \(8\frac{1}{6}:2\frac{1}{2}=\frac{49}{6}:\frac{5}{2}=\frac{49}{6}.\frac{2}{5}=\frac{49}{15}\)

a  17/5*21/7=457/35

b 49/6:21/2=88/126

Chuyển các hỗn số thành p/s rồi thực hiện phép tính (theo mẫu):

a) \(3\frac{2}{5}\times2\frac{1}{7}=\frac{17}{5}\times\frac{15}{7}=\frac{51}{7}\)

b) \(8\frac{1}{6}\div2\frac{1}{2}=\frac{49}{6}\div\frac{5}{2}=\frac{49}{6}\times\frac{2}{5}=\frac{49}{15}\)

\(a,4\dfrac{1}{4}-2=\dfrac{17}{4}-2=\dfrac{9}{4};\dfrac{5}{8}+2\dfrac{3}{5}=\dfrac{5}{8}+\dfrac{13}{5}=\dfrac{129}{40}\\ b,4\dfrac{4}{9}:2=\dfrac{40}{9}\cdot\dfrac{1}{2}=\dfrac{20}{9};\dfrac{2}{3}+3\dfrac{1}{6}=\dfrac{2}{3}+\dfrac{19}{6}=\dfrac{23}{6}\\ c,3\dfrac{1}{5}+2=\dfrac{9}{5}+2=\dfrac{19}{5};\dfrac{3}{5}-2\dfrac{4}{5}=\dfrac{3}{5}-\dfrac{14}{5}=-\dfrac{11}{5}\)

\(d,5\dfrac{1}{7}-2=\dfrac{36}{7}-2=\dfrac{22}{7};\dfrac{4}{5}:1\dfrac{1}{5}=\dfrac{4}{5}:\dfrac{6}{5}=\dfrac{2}{3}\\ e,2\dfrac{3}{5}+1=\dfrac{13}{5}+1=\dfrac{18}{5};\dfrac{1}{4}\cdot2\dfrac{2}{3}=\dfrac{1}{4}\cdot\dfrac{8}{3}=\dfrac{2}{3}\\ f,4\dfrac{1}{3}\cdot1=\dfrac{13}{3};\dfrac{1}{2}+5\dfrac{2}{7}=\dfrac{1}{2}+\dfrac{37}{7}=\dfrac{81}{14}\)

Bài 2: 

a: 2/5=14/35

3/7=15/35

b: -3/4=-9/12

-7/-12=7/12

c: 5/9=60/108

-11/-12=11/12=99/108

d: -4/7=-36/63

8/9=56/63

-10/21=-30/63

Bài 2: 

a: 2/5=14/35

3/7=15/35

b: -3/4=-9/12

-7/-12=7/12

c: 5/9=60/108

-11/-12=11/12=99/108

d: -4/7=-36/63

8/9=56/63

-10/21=-30/63

9 2/7+5 3/7=65/7+38/7=103/7

10 3/10-4 7/10=103/10-47/10=56/10

1. a) Ta có BCNN(12, 15) = 60 nên ta lấy mẫu chung của hai phân số là 60. 

Thừa số phụ:

60:12 =5; 60:15=4

Ta được:

\(\frac{5}{{12}} = \frac{{5.5}}{{12.5}} = \frac{{25}}{{60}}\)

\(\frac{7}{{15}} = \frac{{7.4}}{{15.4}} = \frac{{28}}{{60}}\)

 b) Ta có BCNN(7, 9, 12) = 252 nên ta lấy mẫu chung của ba phân số là 252. 

Thừa số phụ:

252:7 = 36; 252:9 = 28; 252:12 = 21

Ta được:

\(\frac{2}{7} = \frac{{2.36}}{{7.36}} = \frac{{72}}{{252}}\)

\(\frac{4}{9} = \frac{{4.28}}{{9.28}} = \frac{{112}}{{252}}\)

\(\frac{7}{{12}} = \frac{{7.21}}{{12.21}} = \frac{{147}}{{252}}\)

2. a) Ta có BCNN(8, 24) = 24 nên:

\(\frac{3}{8} + \frac{5}{{24}} = \frac{{3.3}}{{8.3}} + \frac{5}{{24}} = \frac{9}{{24}} + \frac{5}{{24}} = \frac{{14}}{{24}} = \frac{7}{{12}}\)

 b) Ta có BCNN(12, 16) = 48 nên:

\(\frac{7}{{16}} - \frac{5}{{12}} = \frac{{7.3}}{{16.3}} - \frac{{5.4}}{{12.4}} = \frac{{21}}{{48}} - \frac{{20}}{{48}} = \frac{1}{{48}}\).