It seems they can be used interchangeably but I am not sure. Can somebody explain the difference of use between these two key words? Where do they become different?
where ever there is a certainty we use in and in uncertainty we use within.
I will come in next week. - Use IN-
I will come within this week - Use within
Also, if some timeframe is allocated ie : do the work in ten minutes
Then if the work is completed in 10 min then use in and if completed before 10 min then within.