Find Serial and parallel percentage of code

Question

If I know the job completion time of a 2 processor system and of a 4 processor system, how do i calculate the time taken(Ts) by a 1 processor system. I want to know this so I can find the serial percentage of any given code using the equation

Ts/Tp = 1/(S+[(1-S)/N])

where S is serial percentage of code and N number of processors

Answer 1

I think time taken would be product of JobCompletionTime and number of processors; jobCompletionTime*n(no of processors);