Bài 1: 

a: \(=\dfrac{4}{8}+\dfrac{2}{8}+\dfrac{1}{8}=\dfrac{7}{8}\)

b: \(=\dfrac{4}{12}+\dfrac{2}{12}+\dfrac{1}{12}=\dfrac{7}{12}\)

B1:

a \(\dfrac{7}{8}\)

b \(\dfrac{7}{12}\)

B2:

a \(\dfrac{3}{7}\)

b \(\dfrac{5}{9}\)

c \(\dfrac{6}{5}\)

B3:

 đội còn phải sửa phần quãng đường nữa  :\(\dfrac{8}{15}\) phần quãng đường

Không rút gọn được nữa đâu em nhé

Ko rút gọn được

Tối giản rồi bn

rút 

gọn

đc

bằng

1/2 

nha

có

1/20

TL:

\(\frac{50}{100}=\frac{50:50}{100:50}=\frac{1}{2}\)

_HT_

Hướng dẫn giải:

\(\dfrac{3}{15}-\dfrac{5}{35}=\dfrac{1}{5}-\dfrac{1}{7}=\dfrac{7}{35}-\dfrac{5}{35}=\dfrac{2}{35}\)

1/5-1/7= 7/35-5/35=2/35

3/15 - 5/35 = 1/5 - 1/7 = 7/35 - 5/35 = 2/35

\(\dfrac{15}{35}=\dfrac{15:5}{35:5}=\dfrac{3}{7}\)

\(\dfrac{24}{27}=\dfrac{24:3}{27:3}=\dfrac{8}{9}\)

\(\dfrac{17}{50}\) ( phân số dã tối giản )

\(\dfrac{15}{45}=\dfrac{15:3}{45:3}=\dfrac{5}{15}=\dfrac{5:5}{15:5}=\dfrac{1}{3}\)

\(\dfrac{99}{121}=\dfrac{99:11}{121:11}=\dfrac{9}{11}\)

`15/35 = (15 \div 5)/(35 \div 5)=3/7`

`24/27 = (24 \div 3)/(27 \div 3)=8/9`

`17/50` đã rút gọn

`15/45=(15 \div 15)/(45 \div 15)=1/3`

`99/121=(99 \div 11)/(121 \div 11)=9/11`

35/21 = 35/21 : 7 = 35 : 7/21 : 7 = 5/3= 15/9

\(\frac{35}{21}=\frac{15}{7}\)

Rút gọn \(\frac{35}{21}=\frac{35:3}{21:3}=\frac{15}{7}\)

\(\frac{35}{21}=\frac{15}{7}\)

Rút gọn : \(\frac{35}{21}=\frac{35\div3}{21\div3}=\frac{15}{7}\)

\(a.-\dfrac{8}{12}=\dfrac{-2\cdot4}{4\cdot3}=-\dfrac{2}{3}\)

\(b.\dfrac{15}{-60}=\dfrac{15}{15\cdot-4}-\dfrac{1}{4}\)

\(c.\dfrac{-16}{-72}=\dfrac{-2\cdot8}{-9\cdot8}=\dfrac{2}{9}\)

\(d.\dfrac{35}{14\cdot15}=\dfrac{7\cdot5}{7\cdot2\cdot5\cdot3}=\dfrac{1}{6}\)

\(\dfrac{8}{12}\)=\(\dfrac{2}{31}\)

\(\dfrac{15}{-60}\)=\(\dfrac{-1}{4}\)

\(\dfrac{-16}{72}\)=\(\dfrac{-2}{9}\)

\(\dfrac{35}{14.15}=\dfrac{35}{210}=\dfrac{1}{6}\)

A

A

A