\(\dfrac{1}{10}+\dfrac{2}{10}+\dfrac{3}{10}+\dfrac{4}{10}+\dfrac{5}{10}+\dfrac{6}{10}+\dfrac{7}{10}+\dfrac{8}{10}+\dfrac{9}{10}=\dfrac{1}{10}.\left(1+2+3+4+5+6+7+8+9\right)\\ =\dfrac{1}{10}.45=\dfrac{45}{10}=\dfrac{45:5}{10:5}=\dfrac{9}{2}\)
\(\dfrac{1}{10}+\dfrac{2}{10}+\dfrac{3}{10}+\dfrac{4}{10}+\dfrac{5}{10}+\dfrac{6}{10}+\dfrac{7}{10}+\dfrac{8}{10}+\dfrac{9}{10}\)
\(=\left(\dfrac{1}{10}+\dfrac{9}{10}\right)+\left(\dfrac{2}{10}+\dfrac{8}{10}\right)+\left(\dfrac{3}{10}+\dfrac{7}{10}\right)+\left(\dfrac{4}{10}+\dfrac{6}{10}\right)+\dfrac{5}{10}\)
\(=1+1+1+1+\dfrac{5}{10}\)
\(=4+\dfrac{5}{10}\)
\(=\dfrac{40}{10}+\dfrac{5}{10}\)
\(=\dfrac{45}{10}\)
⇒ \(\dfrac{1+2+3+4+5+6+7+8+9}{10}=\dfrac{45}{10}=\dfrac{9}{2}\)
Vậy kết quả bằng \(\dfrac{9}{2}\)
#ĐN
`1/10 + 2/10 + 3/10+ 4/10 + 5/10 + 6/10 + 7/10 + 8/10 + 9/10 = ( 1+... 9 )/10 = 45/10 = 9/2`
=\(\dfrac{45}{10}\)=\(\dfrac{9}{2}\)
