Virtual Gate Test Series: Operating System - I/O Operation

Question

Suppose that a process spends a fraction of time P performing CPU activity. With n processes in memory at once, the probability that all n processes are performing I/O operation.

1. $P^{n}$
2. $1-P^{n}$
3. $(1-P)^{n}$
4. $1-(1-P)^{n}$

Answer 1

a process spends a fraction of time P to 

performing a CPU activity. With n processes in memory at once

Then the probability that all n processes are performing I/O operation

Probability=1-P^n

P=fraction of time spent by any process to perform CPU activity

n=of process

Right answer is b: 1-P^n

Comments

All processes should be performing I/O. For each process probability is (1 – P) hence for n processes it shoud be (1 – P)^n i.e option C ?