bạn rút gọn các phân số đó thành các phân số có mẫu là 10 rồi cộng lại thôi

rút gọn hết các ps trong biểu thức, ta được:

 3/10+3/10+3/10+3/10+3/10+3/10+3/10

=21/10

rut gon la duoc ...tich nhe hiha

9/10 nha

=\(\frac{1}{10}\cdot9\)

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

\(\frac{1}{10}+\frac{12}{20}+\frac{3}{30}+\frac{4}{40}+\frac{5}{50}+\frac{6}{60}+\frac{7}{70}+\frac{8}{80}+\frac{9}{90}\)

\(=\frac{1}{10}+\frac{12}{20}+\frac{1}{10}+\frac{1}{10}+\frac{1}{10}+\frac{1}{10}+\frac{1}{10}+\frac{1}{10}+\frac{1}{10}\)

\(=\frac{1}{10}\times8+\frac{12}{20}\)

\(=\frac{4}{5}+\frac{12}{20}\)

\(=\frac{16}{20}+\frac{12}{20}=\frac{28}{20}=\frac{7}{5}\)

 10+20+30+40+50+60+70+80+90

=(10+90)+(20+80)+(30+70)+(40+60)+50

=100 + 100 + 100 + 100 + 50

= 100 x 5 + 50

= 500 + 50 =550

= ( 1 0 + 90) + ( 20 + 80)  + ( 30 + 70) + ( 40 + 6 0) + 50

= 100 + 100 + 100 + 100 + 50

= 400 + 50 

= 450

Vì nguyễn trung hiếu xin **** của Đỗ Tiến

`1/10+2/20+3/30+4/40+5/50+6/60+7/70+8/80+9/90`

`=1/10+1/10+1/10+1/10+1/10+1/10+1/10+1/10+1/10`

`=1/10xx9`

`=9/10`

giúp mình bài này nha

a,đề bài

=1/10+1/10+1/10+1/10+1/10+1/10+1/10+1/10+1/10

=9/10

Phép tính:1/10+1/10+1/10+1/10+1/10+1/10+1/10+1/10+1/10 là rút gọn lần lượt cho 2,3,4,5,6,7,8,9 nha

\(\frac{1}{10}+\frac{2}{20}+\frac{3}{30}+\frac{4}{40}+\frac{5}{50}+\frac{6}{60}+\frac{7}{70}+\frac{8}{80}+\frac{9}{90}\)

=\(\frac{1}{10}+\frac{1}{10}+\frac{1}{10}+\frac{1}{10}+\frac{1}{10}+\frac{1}{10}+\frac{1}{10}+\frac{1}{10}+\frac{1}{10}\)

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

\(\frac{1}{10}+\frac{2}{20}+\frac{3}{30}+\frac{4}{40}+\frac{5}{50}+\frac{6}{60}+\frac{7}{70}+\frac{8}{80}+\frac{9}{90}=\frac{1}{10}+\frac{1}{10}+....+\frac{1}{10}=\frac{9}{10}\)

\(\dfrac{1}{10}+\dfrac{4}{20}+\dfrac{9}{30}+\dfrac{16}{40}+\dfrac{25}{50}+\dfrac{36}{60}+\dfrac{49}{70}+\dfrac{64}{80}+\dfrac{81}{90}\)
\(=\dfrac{1}{10}+\dfrac{1}{5}+\dfrac{3}{10}+\dfrac{2}{5}+\dfrac{1}{2}+\dfrac{3}{5}+\dfrac{7}{10}+\dfrac{4}{5}+\dfrac{9}{10}\)
\(=\left(\dfrac{1}{10}+\dfrac{3}{10}+\dfrac{7}{10}+\dfrac{9}{10}\right)+\left(\dfrac{1}{5}+\dfrac{2}{5}+\dfrac{3}{5}+\dfrac{4}{5}\right)+\dfrac{1}{2}\)
\(=2+2+\dfrac{1}{2}\)
\(=4+\dfrac{1}{2}\)
\(=\dfrac{8}{2}+\dfrac{1}{2}=\dfrac{9}{2}\)

rút gọn mấy phân số trên thì còn

=1/10+1/10+1/10+1/10+1/10+1/10+1/10+1/10+1/10

=9x1/10

=9/10

\(\frac{1}{10}+\frac{2}{20}+\frac{3}{30}+\frac{4}{40}+\frac{5}{50}+\frac{6}{60}+\frac{7}{70}+\frac{8}{80}+\frac{9}{90}\)

\(=\frac{1}{10}+\frac{1}{10}+\frac{1}{10}+\frac{1}{10}+\frac{1}{10}+\frac{1}{10}+\frac{1}{10}+\frac{1}{10}+\frac{1}{10}\)

\(=\frac{1}{10}\times9\)

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

=1/10 + 1/10 +...+ 1/10 ( có 9 phân số )

=9/10

1/10+2/20+3/30+4/40+5/50+6/60+7/70+8/80+9/90

=1/10+1/10+1/10+1/10+1/10+1/10+1/10+1/10+1/10

=1/10*9=9/10

9/10 nha

=1/10+1/10+1/10+1/10+1/10+1/10+1/10+1/10+1/10

=1/10x9

=9/10