Given a CPU time slice of $2$ ms and the following list of processes.

Process	Burst time $($ms$)$	Arrival time
$P1$	$3$	$0$
$P2$	$4$	$2$
$P3$	$5$	$5$

Find average turnaround time and average waiting time using round-robin CPU scheduling.

Time quantum $=2$ ms

Gantt chart:

$P1(0-2),\ P2(2-4),\ P1(4-5),\ P2(5-7),\ P3(7-9),\ P3(9-11),\ P3(11-12)$

Completion time:

$CT(P1)=5$

$CT(P2)=7$

$CT(P3)=12$

Turnaround time:

$TAT=CT-AT$

For $P1$:

$TAT=5-0=5$

For $P2$:

$TAT=7-2=5$

For $P3$:

$TAT=12-5=7$

Average turnaround time:

$\dfrac{5+5+7}{3}=\dfrac{17}{3}=5.66$

Waiting time:

$WT=TAT-BT$

For $P1$:

$WT=5-3=2$

For $P2$:

$WT=5-4=1$

For $P3$:

$WT=7-5=2$

Average waiting time:

$\dfrac{2+1+2}{3}=\dfrac{5}{3}=1.66$