Question

[Hoàng Linh]

1/3 + 16 + 1/10 + 1/15 + 1/21 + 1/28

bạn nào làm đúng và nhanh nhất mình sẽ tich cho bạn đó

Answer 1

[Nguyễn Trọng Vũ Hùng]

\(\frac{1}{3}+\frac{1}{6}+\frac{1}{10}+\frac{1}{15}+\frac{1}{21}+\frac{1}{28}\)

\(=\frac{2}{6}+\frac{2}{12}+\frac{2}{20}+\frac{2}{30}+\frac{2}{42}+\frac{2}{56}\)

\(=\frac{2}{2\text{x}3}+\frac{2}{3\text{x}4}+\frac{2}{4\text{x}5}+\frac{2}{5\text{x}6}+\frac{2}{6\text{x}7}+\frac{2}{7\text{x}8}\)

\(=2\text{x}\left(\frac{1}{2}-\frac{1}{3}+\frac{1}{3}-\frac{1}{4}+\frac{1}{4}-\frac{1}{5}+\frac{1}{5}-\frac{1}{6}+\frac{1}{6}-\frac{1}{7}+\frac{1}{7}-\frac{1}{8}\right)\)

\(=2\text{x}\left(\frac{1}{2}-\frac{1}{8}\right)\)

\(=2\text{x}\frac{3}{8}=\frac{3}{4}\)

Answer 2

[Hoàng Linh]

thank you bạn