a) Ta có: \(\dfrac{9}{5}:\dfrac{17}{5}+\dfrac{8}{5}:\dfrac{17}{15}\)

\(=\dfrac{9}{5}\cdot\dfrac{5}{17}+\dfrac{8}{5}\cdot\dfrac{15}{17}\)

\(=\dfrac{9}{17}+\dfrac{24}{17}=\dfrac{33}{17}\)

 a )9/5: 17/5 + 8/5 : 17/15 = 9/5 x 5/17 + 8/5 x 15/17 = 9/17  +24/17=  33/17

b) ?

a) 19/35+15/19+16/35+23/19+4/15+11/15 = (19/35+16/35)+(15/19+23/19)+(4/15+11/15) = 1+2+1 = 4 b)4/17-7/15+13/17-8/15+5/8-7/16 = (4/17+13/17)-(7/15-8/15)+(5/8-7/16) = 1-1+3/16 =3/16

A )  2/17 + 30/46 + 15/17 + 4/49 + 8/23=102/49

B ) 5/8 x ( 19/31 x 8/5 )=19/31

C ) 7/9 x 8/15 x 9/7 x 15/4=2

D ) 11/12 x 24/7 x 21/22=3

nhìu quá nên mk chỉ cho kết quả thôi nha ^-^!!!

a.1+3+5+7+9+11+13+15+17+19

muốn tính tổng của dãy ta lấy tổng số đầu và cuối nhân số các số hạng rồi chia 2.

tổng của dãy:(19+1)x10:2=100

a) 11/15 + 5/7 + 2/7 + 4/15

= ( 11/15 + 4/15 ) + ( 5/7 + 2/7 )

= 1 + 1 

= 2

b ) 5/9 x 1/2 + 5/9 x 6/4

= 5/9x ( 1/2 + 6/4 )

= 5/9 x 2

= 10/9

c) 7/8 : 1/2 + 9/8 : 1/2

= ( 7/8 + 9/8 ) ; 1/2

= 2 : 1/2

= 4

d) 17/10 + 1/2 - 7/10

= ( 17/10 - 7/10 ) + 1/2

= 1 + 1/2

= 3/2

ĐA : a  nha bn 

#ht#

\(\frac{17}{8}+\frac{28}{15}-\frac{8}{15}=\frac{17}{8}+\frac{4}{3}=\frac{83}{24}=3\frac{11}{24}\)

=> chọn a

Đáp án : a) 311/24

1/2 + 1/3 + 1/4 = 6/12 + 4/12 + 3/12 = 13/12

2/3 + 3/4 + 4/5 = 8/12 + 9/12 + 4/5 = 17/12 + 4/5 = 85 / 60 +  48 / 60 = 133/ 60

6/5 + 4/3 + 7/9 = 18/ 15 + 20/15 + 7/9 = 38 /15 + 7/ 9 = 114/45 +35/45 = 149/45

8/9 - 5/6 = 16/18 - 15/18 = 1/18 

15/17 - 11 /13 = 195/221 -187/221= 8/221

a) \(\frac{1}{2}+\frac{1}{3}+\frac{1}{4}\)

= \(\frac{6}{12}+\frac{4}{12}+\frac{3}{12}\)

= \(\frac{13}{12}\).

b) \(\frac{2}{3}+\frac{3}{4}+\frac{4}{5}\)

= \(\frac{8}{12}+\frac{9}{12}+\frac{4}{5}\)

= \(\frac{17}{12}+\frac{4}{5}\)

= \(\frac{85}{60}+\frac{48}{60}\)

= \(\frac{133}{60}\).

c)\(\frac{6}{5}+\frac{4}{3}+\frac{7}{9}\)

= \(\frac{54}{45}+\frac{62}{45}+\frac{35}{45}\)

= \(\frac{151}{45}\).

d) \(\frac{8}{9}-\frac{5}{6}\)

= \(\frac{16}{18}-\frac{15}{18}\)

= \(\frac{1}{18}\).

e) \(\frac{15}{17}-\frac{11}{13}\)

= \(\frac{195}{221}\)\(-\frac{187}{221}\)

= \(\frac{8}{221}\).