2 câu trả lời
`1/61+1/62+1/63+...+1/100`
Ta có `1/61 < 1/60`
`1/62 < 1/60`
`...`
`1/100 <1/60`
⇒ `1/61+1/62+1/63+...+1/100 < 1/60 +1/60 +....+ 1/60` ( có 40 số 1/60)
`⇒ 1/61+1/62+1/63+...+1/100 < 40/60=2/5`
`1/61+1/62+1/63+...+1/100`
Ta có `1/61 < 1/60`
`1/62 < 1/60`
`...`
`1/100 <1/60`
⇒ `1/61+1/62+1/63+...+1/100 < 1/60 +1/60 +....+ 1/60` ( có 40 số 1/60)
`⇒ 1/61+1/62+1/63+...+1/100 < 40/60=2/5`