A worm climbs a rod by 5cms in one second and falls by 2cm next second. How many seconds it will take to climb 60cms rod?
after n seconds, he has climbed 3n cm.
After 19 seconds he has climbed 57cm
On the 20th second he's at the top.
After 19 seconds he has climbed 57cm
On the 20th second he's at the top.