Bạn ơi $\frac{2}{59.62}$ nhé.
S= $\frac{2}{2.5}$ + $\frac{2}{5.8}$ + $\frac{2}{8.11}$ + ... + $\frac{2}{59.62}$
1,5.S=1,5.($\frac{2}{2.5}$ + $\frac{2}{5.8}$ + $\frac{2}{8.11}$ + ... + $\frac{2}{59.62}$)
1,5.S=$\frac{3}{2.5}$ + $\frac{3}{5.8}$ + $\frac{3}{8.11}$ + ... + $\frac{3}{59.62}$
1,5.S=$\frac{1}{2}$ - $\frac{1}{5}$ + $\frac{1}{5}$ - $\frac{1}{8}$ + ... + $\frac{1}{59}$ - $\frac{1}{62}$
1,5.S=$\frac{1}{2}$ - $\frac{1}{62}$
1,5.S=$\frac{15}{31}$
S=$\frac{10}{31}$
Vậy $\frac{2}{2.5}$ + $\frac{2}{5.8}$ + $\frac{2}{8.11}$ + ... + $\frac{2}{59.62}$= $\frac{10}{31}$