=(1/11+10/11)+(2/11+9/11)+(3/11+8/11)+(4/11+7/11)+(5/11+6/11)

=11/11+11/11+11/11+11/11+11/11

=1+1+1+1+1

=5

=1+2+3+4+5+6+7+8+9+10 trên 11

= (1+9)+(2+8)+3+7)+(4+6)+5+10 trên 11

=10+10+10+10+10+5 trên 11

=10x5+5 trên 11

=50+5 trên 11

=55/11

=5

trên có nghĩa là (tất cả) phần 11 nha.

1/11+2/11+3/11+4/11+5/11+6/11+7/11+8/11+9/11+10/11

=(1/11+10/11)+(2/11+9/11)+(3/11+8/11)+(4/11+7/11)+(5/11+6/11)

=1+1+1+1+1

=5

chúc bạn học tốt!

ai cứu với ạ

ko 

có chết đâu mà phải cứu

1,

a,=4/7:4/9.3

=9/7.3

=27/7

b,=(7/11+4/11).5/6

=1.5/6

=5/6

`(6/7-2/7):4/9xx3=4/7xx9/4xx3=[4xx9xx3]/[7xx4]=27/7`

`7/11xx5/6+4/11xx5/6=(7/11+4/11)xx5/6=11/11xx5/6=5/6`

a) 5/11 + 4/7 + 6/11 + 10/7 = (5/11 + 6/11) + (4/7 + 10/7)

                                          = 1 + 2 = 3

b) 15/9 + 5/8 - 5/9 + 11/8 = (15/9 - 5/9) + (5/8 + 11/8)

                                        = 10/9 + 2 = 28/9

c) 21/12 + 4/11 + 7/11 - 11/12 = (21/12 - 11/12) + (4/11 + 7/11)

                                               = 10/12 + 1 = 11/6

nhóm từng cai có cùng mẫu số với nhau rồi cộng tử số lại là được

A) \(\frac{5}{11}+\frac{4}{7}+\frac{6}{11}+\frac{10}{7}\)

\(=\left(\frac{5}{11}+\frac{6}{11}\right)+\left(\frac{4}{7}+\frac{10}{7}\right)\)

\(=1+2=3\)

B) \(\frac{15}{9}+\frac{5}{8}-\frac{5}{9}+\frac{11}{8}\)

\(=\left(\frac{5}{8}+\frac{11}{8}\right)+\left(\frac{15}{9}-\frac{5}{9}\right)\)

\(=2+\frac{10}{9}=2\frac{10}{9}\)

C) \(\frac{21}{12}+\frac{4}{11}+\frac{7}{11}-\frac{11}{12}\)

\(=\left(\frac{21}{12}-\frac{11}{12}\right)+\left(\frac{4}{11}+\frac{7}{11}\right)\)

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

CHÚC BẠN HỌC TỐT!!

\(\dfrac{9}{4}\times\dfrac{15}{11}+\dfrac{3}{4}:\dfrac{11}{7}-\dfrac{3}{4}\times\dfrac{8}{11}\)
\(=\dfrac{3}{4}\times3\times\dfrac{15}{11}+\dfrac{3}{4}\times\dfrac{7}{11}-\dfrac{3}{4}\times\dfrac{8}{11}\)
\(=\dfrac{3}{4}\times\dfrac{45}{11}+\dfrac{3}{4}\times\dfrac{7}{11}-\dfrac{3}{4}\times\dfrac{8}{11}\)
\(=\dfrac{3}{4}\times\left(\dfrac{45}{11}+\dfrac{7}{11}-\dfrac{8}{11}\right)\)
\(=\dfrac{3}{4}\times4\)
\(=3\)

`9/4xx15/11+3/4:11/7-3/4xx8/11`

`=3/4xx15/11xx3+3/4xx7/11-3/4xx8/11`

`=3/4xx45/11+3/4xx7/11-3/4xx8/11`

`=3/4xx(45/11+7/11-8/11)`

`=3/4xx4`

`=3`

`5/9+5/11+4/9+4/11+2/11`

`=(5/9+4/9)+(5/11+4/11+2/11)`

`=9/9+11/11`

`=1+1`

`=2`

= (5/9 + 4/9) + (5/11 + 4/11 + 2/11)

= 9/9 + 11/11 = 2

= 2

\(\dfrac{3}{11}\text{×}\dfrac{7}{19}+\dfrac{3}{11}\text{×}\dfrac{10}{19}+\dfrac{3}{11}\text{×}\dfrac{1}{19}=\dfrac{3}{11}\text{×}\left(\dfrac{7}{19}+\dfrac{10}{19}+\dfrac{2}{19}\right)=\dfrac{3}{11}\text{×}1=\dfrac{3}{11}\)