5/5 x 10 + 5/10 x 15 + 5/15 x 20 + 5/20 x 25 +...+ 5/95 x 100

`5/(5xx10) + 5/(10 xx 15) + 5/(15xx20) + 5/(20xx25)+...+5/(95 xx100)`

`= (10-5)/(5xx10) + (15-10)/(10xx15) + (20-15)/(15xx20) + (25-20)/(20xx25) +...+(100-95)/(95xx100)`

`= 1/5 - 1/10 + 1/10 - 1/15 + 1/15 - 1/20 +....+ 1/95- 1/100`

`= 1/5 - 1/100`

`= 20/100 - 1/100`

`= 19/100`