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

`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

 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

\(\frac{1}{10}+\frac{4}{20}+\frac{9}{30}+\frac{16}{40}+\frac{25}{50}\) \(+\frac{36}{60}+\frac{49}{70}+\frac{64}{80}+\frac{81}{90}\)

\(=\frac{1}{10}+\frac{1}{5}+\frac{3}{10}+\frac{2}{5}+\frac{1}{2}+\frac{3}{5}+\frac{7}{10}+\frac{4}{5}+\frac{9}{10}\)

\(=\left(\frac{1}{10}+\frac{9}{10}\right)+\left(\frac{1}{5}+\frac{4}{5}\right)+\left(\frac{3}{10}+\frac{7}{10}\right)+\left(\frac{2}{5}+\frac{3}{5}\right)+\frac{1}{2}\)

\(=1+1+1+1+0,5\)

\(=4+0,5\)

\(=4,5\)

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

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

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

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

50 + 30 + 60 + 40 + 50 + 70 + 120 + 80 + 215 + 85 + 95 + 5 + 12 + 73+ 27 + 88 

= (50 + 50 ) + (60 + 40) + (70 + 30) + (120 + 80) + (95 + 5) + (73 + 27) + (12 + 88) + (215 + 85)

= 100 + 100 + 100 + 200 + 100 + 100 + 100 + 300

= 1100

9/10 nha

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

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

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

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

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

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

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

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

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