ISRO CSE 2011 | Question: 77

Question

In a system using single processor, a new process arrives at the rate of six processes per minute and each such process requires seven seconds of service time. What is the CPU utilization?

• A. 70%
• B. 30%
• C. 60%
• D. 64%

Comments

Can u pls explain this

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Totel no of second cpu work is 6*7=42second

Cpu utillisation= (42/60)*100= 70%

Answer A

Answer 1

There are six process coming in one minute and each process require $7sec$.

So $\text{CPU utilization}=\frac{\text{Useful Time}}{\text{Total time}}$

So CPU will be busy for $42 sec$ to service each process within one minute. This will be a useful time.

So $\text{CPU utilization} =\frac{42}{60}\times 100$

                             =70%

Comments

total time=60? why?

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Data is given for No of processes per minute which 60 sec. CPU is running for 42 sec.

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Alternative approach –

If process bt is 7sec, then in 1 min we can ideally complete execution of 60/7 = 8.57 jobs, but we are only executing 6 jobs.

So cpu utilization = (6/8.57)x 100 = 70%