$\frac{1}{12}$ + $\frac{2}{24}$ + $\frac{3}{54}$ + $\frac{4}{117}$ + $\frac{5}{234}$
=$\frac{1}{12}$ + $\frac{1}{12}$ + $\frac{3}{54}$ + $\frac{4}{117}$ + $\frac{5}{234}$
= $\frac{2}{12}$ + $\frac{3}{54}$ + $\frac{4}{117}$ + $\frac{5}{234}$
= $\frac{1}{6}$+ $\frac{3}{54}$ + $\frac{4}{117}$ + $\frac{5}{234}$
= ($\frac{9}{54}$ + $\frac{3}{54}$) +($\frac{8}{234}$ + $\frac{5}{234}$)
= $\frac{12}{54}$ + $\frac{13}{234}$
=$\frac{2808}{12636}$ + $\frac{702}{12636}$
= $\frac{3510}{12636}$= $\frac{5}{18}$
(hết cách rồi)
