a) \(\dfrac{5}{9}+\dfrac{13}{7}+\dfrac{15}{13}+\dfrac{8}{7}+\dfrac{4}{9}+\dfrac{11}{13}\)

\(=\left(\dfrac{5}{9}+\dfrac{4}{9}\right)+\left(\dfrac{13}{7}+\dfrac{8}{7}\right)+\left(\dfrac{15}{13}+\dfrac{11}{13}\right)\)

\(=1+3+2\)

\(=6\)

b) \(\dfrac{3}{5}+\dfrac{18}{9}+\dfrac{4}{10}\)

\(=0,6+2+0,4\)

\(=\left(0,6+0,4\right)+2\)

\(=1+2\)

\(=3\)

\(a\dfrac{5}{9}+\dfrac{4}{9}+\dfrac{13}{7}+\dfrac{8}{7}+\dfrac{15}{13}+\dfrac{11}{13}=\dfrac{9}{9}+\dfrac{21}{7}+\dfrac{26}{13}=1+3+2=6\)

450 nha !

= 450

a. 60x17/20=51

b.5/6x12/35=2/7

c.1/9

a) 60 x 17/20= 51

b) 5/6 x 12/35 = 2/7

c) 1/9

\(a.\dfrac{3}{4}=\dfrac{3.9}{4.9}=\dfrac{27}{36}\)

\(\dfrac{5}{9}=\dfrac{5.4}{9.4}=\dfrac{20}{36}\)

\(b.\dfrac{5}{6}=\dfrac{5.3}{6.3}=\dfrac{15}{18}\) 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

3.<,>,=

3-5/6....>...1+5/6          41/60-11/60....=....3/8+1/8
2/5+4/15....>...9/10-3/5        1/3-1/12..<....7/8-5/16

CẢM ƠN

a)3/46;8/46;9/9;9/7

b)9/10;6/6;8/7;6/7

c)20/9;60/60;4/5;5/8

giải thích giõ ví dụ :

ta quy đống : .....................................................được

mà :  ...........................................................nên  ..................................

vậy các phân số được viết theo thứ tự :......................................................

a) 21: 25 =\(\dfrac{21}{25}\)

30: 43 = \(\dfrac{30}{43}\)              

61: 69 = \(\dfrac{61}{69}\) 

17: 100 = \(\dfrac{17}{100}\)

b)9 : 4 = \(\dfrac{9}{4}\)

51: 7 = \(\dfrac{51}{7}\)

60 : 39 = \(\dfrac{60}{39}\)                  

200 : 163 = \(\dfrac{200}{163}\)

\(a.60\times\left(\frac{7}{12}+\frac{4}{15}\right)\)

\(=60\times\left(\frac{35}{60}+\frac{16}{60}\right)\)

\(=60\times\frac{51}{60}\)

\(=51\)

\(b.\frac{1}{2}\times\frac{2}{3}\times\frac{3}{4}\times\frac{4}{5}\times\frac{5}{6}\times\frac{6}{7}\times\frac{7}{8}\times\frac{8}{9}\)

\(=\frac{1\times2\times3\times4\times5\times6\times7\times8}{2\times3\times4\times5\times6\times7\times8\times9}\)

\(=\frac{1}{9}\)