A frog is at the bottom of the well which is 20 meters deep. - with Answer

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?

Solution:

First day it jumps 5 meters and falls 4 meters. Now it will be at a height of 1 meter.

Second day, it jumps to 6 meters and falls back to 2 meters.

Third day it jumps to 7 meters and falls back to 3 meters.

          .......

Fifteenth day it jumps to 19 meters and falls back to 15 meters.

Finally, sixteenth day it jumps to 20 meters, but now the frog has reached the top of the well.

So the Frog reaches the top of the well as the sixteenth day.