a: 13/35=1/5+1/7+1/35

b: 17/63=1/9+1/7+1/63

a: 13/35=1/5+1/7+1/35

b: 17/63=1/9+1/7+1/63

a: \(\dfrac{5}{3}\cdot\dfrac{4}{5}=\dfrac{4}{3}\)

b: \(\dfrac{2}{3}\cdot\dfrac{3}{5}=\dfrac{2}{5}\)

c: \(\dfrac{7}{6}\cdot\dfrac{6}{5}=\dfrac{7}{5}\)

d: \(\dfrac{8}{5}\cdot\dfrac{5}{7}=\dfrac{8}{7}\)

e: \(\dfrac{7}{6}\cdot\dfrac{6}{7}=\dfrac{7}{7}=1\)

g: \(\dfrac{9}{5}\cdot\dfrac{5}{2}=\dfrac{9}{2}\)

h: \(\dfrac{4}{3}\cdot\dfrac{3}{5}=\dfrac{4}{5}\)

\(a,\dfrac{13}{4}\times\dfrac{2}{3}\times\dfrac{4}{13}\times\dfrac{3}{2}=\left(\dfrac{13}{4}\times\dfrac{4}{3}\right)\times\left(\dfrac{2}{3}\times\dfrac{3}{2}\right)=1\times1=1\)

\(b,\dfrac{75}{100}+\dfrac{18}{21}+\dfrac{19}{32}+\dfrac{1}{4}+\dfrac{3}{21}+\dfrac{13}{32}=\left(\dfrac{3}{4}+\dfrac{1}{4}\right)+\left(\dfrac{18}{21}+\dfrac{3}{21}\right)+\left(\dfrac{19}{32}+\dfrac{13}{32}\right)=1+1+1=3\\ c,\dfrac{4}{7}\times\dfrac{5}{6}+\dfrac{4}{7}\times\dfrac{1}{6}=\dfrac{4}{7}\times\left(\dfrac{5}{6}+\dfrac{1}{6}\right)=\dfrac{4}{7}\times1=\dfrac{4}{7}\\ d,\dfrac{3}{5}\times\dfrac{7}{9}-\dfrac{3}{5}\times\dfrac{2}{9}=\dfrac{3}{5}\times\left(\dfrac{7}{9}-\dfrac{2}{9}\right)=\dfrac{3}{5}\times\dfrac{5}{9}=\dfrac{1}{3}\)

\(e,\dfrac{5}{9}\times\dfrac{1}{4}+\dfrac{4}{9}\times\dfrac{3}{12}=\dfrac{5}{9}\times\dfrac{1}{4}+\dfrac{4}{9}\times\dfrac{1}{4}=\dfrac{1}{4}\times\left(\dfrac{5}{9}+\dfrac{4}{9}\right)=\dfrac{1}{4}\times1=\dfrac{1}{4}\\ f,\dfrac{7}{9}\times\dfrac{8}{5}\times\dfrac{3}{5}=\dfrac{56}{75}\\ g,\dfrac{2}{5}\times\dfrac{3}{4}+\dfrac{3}{4}\times\dfrac{3}{5}=\dfrac{3}{4}\times\left(\dfrac{2}{5}+\dfrac{3}{5}\right)=\dfrac{3}{4}\times1=\dfrac{3}{4}\\ h,\dfrac{2006}{2005}\times\dfrac{3}{4}-\dfrac{3}{4}\times\dfrac{1}{2005}=\dfrac{3}{4}\times\left(\dfrac{2006}{2005}-\dfrac{1}{2005}\right)=\dfrac{3}{4}\times1=\dfrac{3}{4}\)

a: \(=\dfrac{13}{4}\cdot\dfrac{4}{13}\cdot\dfrac{2}{3}\cdot\dfrac{3}{2}=1\cdot1=1\)

b: \(=\dfrac{3}{4}+\dfrac{1}{4}+\dfrac{6}{7}+\dfrac{1}{7}+\dfrac{19}{32}+\dfrac{13}{32}=1+1+1=3\)

c: \(=\dfrac{4}{7}\left(\dfrac{5}{6}+\dfrac{1}{6}\right)=\dfrac{4}{7}\)

d: \(=\dfrac{3}{5}\left(\dfrac{7}{9}-\dfrac{2}{9}\right)=\dfrac{3}{5}\cdot\dfrac{5}{9}=\dfrac{1}{3}\)

e: \(=\dfrac{1}{4}\left(\dfrac{5}{9}+\dfrac{4}{9}\right)=\dfrac{1}{4}\)

C

C

c. 27/7 nha bn

a)8/25 ;  9/25 ; 12/25; 24/25

b)7/3 ; 7/9 ;7/8 ; 7/26

c)3/5 ; 9/10; 14/15; 23/30

d)5/9; 11/15 ; 11/18 ;14/15

Chiều cao mảnh vườn là:

                  12 x \(\dfrac{2}{3}\) = 8 (m)

Diện tích mảnh vườn là:

                  12  x 8 = 96 ( m²)

                             ĐS: 96 m²

Tổng hai phân số ban đầu là

7/9+1/5=35/45+9/45=44/45

7/9+1/5=35/45+9/45=44/45

a: =1/3x7/5=7/15

b: =11/9x1/2=11/18

c: =1/3x3/4=1/4

d: =1/5x4/5=4/25

e: =2/3x1/4=2/12=1/6

f: =1/2x1/3=1/6

g: =1/3x1/2=1/6