Question

[Nguyễn Đình Dũng]

Điền dấu ( > ; < ; = ) vào chỗ trống

\(\frac{1}{41}+\frac{1}{42}+\frac{1}{43}+.....+\frac{1}{79}+\frac{1}{80}\)  \(.........\) \(\frac{5}{6}\)

khó quá nghĩ mãi không ra

Answer 1

[Lê Chí Cường]

Ta thấy: 1/41+1/42+…+1/60<1/40.20=1/2

            1/61+1/62+…+1/80<1/60.20=1/3

=>1/41+1/42+…+1/80<1/2+1/3=5/6

Vậy \(\frac{1}{41}+\frac{1}{42}+...+\frac{1}{80}<\frac{5}{6}\)

Answer 2

[Ngọc Nguyễn Minh]

\(\frac{1}{41}+\frac{1}{42}+\frac{1}{43}+....+\frac{1}{80}>\frac{40}{41}>\frac{5}{6}\)