Question

A frog is at the bottom of the 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

20 days 
jumps 5m
falls 4m
therefore,distance covered in 1 day= 5-4
=1m
let no of days to cover 20m be x
therefore days taken to cover 20m = 20 *1
=20 days
it will take 20 days for frog

Answer 2

If we apply logic answer is 16days.
the frog jump every day 5-4=1m
so the distance covered
first day=1m
second day=2m
third day =3m
and so on.
but on 15th day =15m
and on 16th day=20m
as every day he jump 5m and slip 4m due to wall