A puzzle 5
A biology scientist was studying one of the types of micro-organisms,
he put one of them on an empty Microscope slide,
After 20 seconds , it split into 2 ,
After other 20 seconds , the 2 split into 4 ,
and so on.
After an hour , the slide became semi-filled.
How long more (in seconds) will it take the slide to become fully filled ?