Question

Các bạn giải bài này giúp mình với

1/30+2/30+...+8/30+9/30

 

Answer 1

\(\frac{1}{30}+\frac{2}{30}+...+\frac{9}{30}\)

\(=\frac{1+2+...+9}{30}\)

\(=\frac{\left(9+1\right)\cdot9\div2}{30}\)

\(=\frac{45}{30}=\frac{3}{2}\)

Answer 2

\(\frac{1}{30}+\frac{2}{30}+...+\frac{8}{30}+\frac{9}{30}\)

\(\Rightarrow\frac{9\left(\frac{9+1}{2}\right)}{30}\)

\(\Rightarrow\frac{9\cdot5}{30}=\frac{45}{30}\)

\(\Rightarrow\frac{3}{2}\)