Question

A frog is at the bottom of a well which is 20 meters deep. Everyday the frog jumps 5 meters upwards and fall 4 meters down. How many days it will take for the frog to reach the top?

Answer 1

Everyday frog jump 5 meters but falls 4 meters down,
means net upward = 1 meter in 1 day
It will take 15 days to jump up to 15 meters
after that, final jump = 5 meters, frog is out of the well, then no slipping .
So, total number of days = 15 +1 = 16 days

Answer 2

frog jumps 5 meters but fall 4 meters means 1 meter each day
last jump will be made at once and it will be out of well 
20-5=15
15 meters 15 days last jump one day
16 days