title: How to calculate execution time (speedup)
body: <p>I was stuck when trying to calculate for the speedup. So the question given was:</p>
  
  <hr>
  
  <p><strong>Question 1</strong></p>
  
  <p><em>If 50% of a program is enhanced by 2 times and the rest 50% is enhanced by 4 times then what is the overall speedup due to the enhancements? Hints: Consider that the execution time of program in the machine before enhancement (without enhancement) is T. Then find the total execution time after the enhancements, T'. The speedup is T/T'.</em></p>
  
  <hr>
  
  <p>The only thing I know is speedup = execution time before enhancement/execution time after enhancement. So can I assume the answer is:</p>
  
  <p>Speedup = T/((50/100x1/2) + (50/100x1/4))</p>
  
  <p>Total execution time after the enhancement = T + speedup</p>
  
  <p>(50/100x1/2) because 50% was enhanced by 2 times and same goes to the 4 times.</p>
  
  <hr>
  
  <p><strong>Question 2</strong></p>
  
  <p><em>Let us hypothetically imagine that the execution of (2/3)rd of a program could be made to run infinitely fast by some kind of improvement/enhancement in the design of a processor. Then how many times the enhanced processor will run faster compared with the un-enhanced (original) machine?</em> </p>
  
  <p>Can I assume that it is 150 times faster as 100/(2/3) = 150</p>
  
  <p>Any ideas? Thanks in advance.</p>