Defining Performance (Cont.)

The phrase “X is n times faster than Y” or “X is n times as fast as Y” means 
   PerformanceX / PerformanceY = n
If X is n times as fast as Y, then the execution time on Y is n times as longer as it is on X: 
   PerformanceX / PerformanceY 

 = Execution timeY / Execution timeX  = n

Relative Performance
If computer A runs a program in 10 seconds and computer B runs the same program in 25 seconds, how much faster is A than B?  

In the above example, we could also say that computer B is 2.5 times slower than computer A, since 
   PerformanceA / PerformanceB = 2.5
means that 
   PerformanceA / 2.5 = PerformanceB
Question: Assume computer A is 3 times as fast as computer B. If computer A runs a program in 30 seconds, how much time does the computer B require to run the same program?

Answer:   seconds