bài 5

a) 

`7/5xx15/14`

`=105/70=3/2`

b)

`8/15xx25/8`

`=200/120=5/3`

c)

`2/15xx5/22`

`=10/330`

`=1/33`

bài 6

chiều rộng cx là đơn vị m phải ko ạ?

diện tích căn phòng là

`11/2xx7/2=77/4(m^2)`

`2/5 + 9/15= 2/5 + 3/5=5/5=1`

`15/45 + 25/30= 1/3 + 5/6= 2/6+5/6=7/6`

`28/32 + 45/72=7/8+ 5/8=12/8=3/2`

`8/28 + 5/30= 2/7 + 1/6= 12/42 + 7/42= 19/42`

a) \(\dfrac{25}{60}+6\times\dfrac{1}{8}=\dfrac{25}{60}+\dfrac{3}{4}=\dfrac{25}{69}+\dfrac{45}{60}=\dfrac{25+45}{60}=\dfrac{70}{60}=\dfrac{7}{6}\)

b) \(\dfrac{15}{9}\times\left(6:\dfrac{30}{9}\right)=\dfrac{15}{9}\times\left(6\times\dfrac{30}{9}\right)=\dfrac{15}{9}\times20=\dfrac{100}{3}\)

mn ơi e vít nhầm là tính rồi rút gọn mn sửa lại là rút gọn rùi tính

a: =2/5+3/5=1

b: =1/3+5/6=2/6+5/6=7/6

c: =7/8+5/8=12/8=3/2

d: =2/3+2/10

=20/30+6/30

=26/30=13/15

e: =1/2+1/3

=3/6+2/6

=5/6

f: =2/7+1/6

=12/42+7/42

=19/42

Nay rảnh lại qua làm mấy bài lớp 4 ^^

Tui làm luôn kh ghi đề nhá

1, 

\(\frac{2}{3}+\frac{8}{15}=\frac{6}{5}\)

\(\frac{2}{5}+\frac{2}{3}=\frac{16}{15}\)

\(\frac{2}{3}+\frac{5}{6}=\frac{3}{2}\)

2, 

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

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

\(=1+\frac{6}{5}\)

\(=\frac{11}{5}\)

\(\cdot\frac{6}{4}+\frac{7}{3}+\frac{4}{4}+\frac{3}{3}\)

\(=\frac{6}{4}+\frac{4}{4}+\frac{7}{3}+\frac{3}{3}\)

\(=\frac{10}{4}+\frac{10}{3}\)

\(=\frac{35}{6}\)

2, 

b: 12/20+6/18=3/5+1/3=9/15+5/15=14/15

c: 8/12+20/30=2/3+2/3=4/3

d: 10/12+12/36=5/6+2/6=7/6

a) 2/5+9/5=11/5

b) 15/45+25/30=7/6

c) 28/32+45/72=3/2

d) 8/28+5/30=19/42

bài 2

a) x - 4/5 =4/5 + (3/7+3/5)

x-4/5=4/5+36/35

x-4/5=64/35

x=64/35+4/5

x=92/35

b) x-7/35=4/5

x=4/5+7/35

x=1

nhớ tk m nhé

a = 18/5

b = 3/9 + 5/6 = 6/18 + 25/18  = 31/18

c = 7/8 + 5/8 = 12/8

d = 4/14 + 1/6 = 14/42 + 7/42 = 21/42 -= 7/14

b2

x - 4/5 = 4.5 + ( 3/7 + 3/5 )

x - 4/5 = 49/35

           x = 49/35 + 4/5

              x = 77/35

x - 7/35 = 4/5

             x = 4/5 + 7/35

                 x = 1

mình ko chắc chắn đâu

mình nghĩ mình làm sai

xin lỗi làm nhầm

a: =1/4+1/4=2/4=1/2

b: =3/5+3/5=6/5

c: =5/9+7/9=12/9=4/3

a, 1/4+1/4=2/4=1/4

b, 3/5+3/5=6/5

c, 5/9+7/9=12/9=4/3

a)1/4+1/4=2/4=1/4

b) 3/5+3/5=6/5

c) 5/9+7/9=12/9=4/3

b)15/25+6/21=3/5+2/7=31/35 nha bạn

a, \(\frac{5}{16}+\frac{3}{8}=\frac{5}{16}+\frac{6}{16}=\frac{11}{16}\)

b, \(\frac{15}{25}+\frac{6}{21}=\frac{3}{5}+\frac{2}{7}\)

                           \(=\frac{21}{35}+\frac{10}{35}=\frac{31}{35}\)

a) Ta có: \(\frac{5}{16}+\frac{3}{8}=\frac{5}{16}+\frac{6}{16}=\frac{11}{16}\)

b) Ta có: \(\frac{3}{5}+\frac{2}{7}=\frac{21}{35}+\frac{10}{35}=\frac{31}{35}\)

12/18 + 12/42 = 2/3 + 2/7 = 14/21 + 6/21 = 20/21

1/2 + 2/4 + 3/6 + 4/8 + 5/10 + 6/12

= 1/2 + 1/2 + 1/2 + 1/2 + 1/2 + 1/2

= 1/2 x 6

=6/2

=3

Còn phần D thì sao😶

tra hieu gi ca