Đáp án:
Giải thích các bước giải:
$\frac{1.2.5+3.4.15+4.8.20+7.14.350}{2.5.11+6.10.33+8.20.44+14.35.770}$
= $\frac{1+1.4.15+4.1+1.1.1}{1.11+6.10.33+1.1.11+1.11}$ (Rút gọn)
= $\frac{1+4.15+4.1+1}{11+6.10.33+1.11+1.11}$
= $\frac{1+4.(15+1)+1}{11.(1+1+1)+6.10.33}$
= $\frac{1+4.16+1}{11.3+6.10.33}$
= $\frac{1+64+1}{33.1+60.33}$
= $\frac{66}{33.(1+60)}$
= $\frac{66}{33.61}$
= $\frac{66}{2013}$
= $\frac{2}{61}$