Answer:
Number of planes on the runway or waiting to take off is approximately 2
Step-by-step explanation:
Given the data in the question;
On average there are 21 planes taking off per hour
rate of flow = frequency of take off = 21 planes / hr
= 21 planes per 60 minutes
= 0.35 planes/min
Now, we get the throughput time
throughput time = total time for take off = waiting time on runway + run time on runway
= (4 minutes and 21 seconds) + 27 seconds
= 4.35 minutes + 0.45 minutes
= 4.8 minutes
Now, using Little's law;
Number of planes on the runway or waiting to take off will be;
N = Rate of flow × throughput time
we substitute
N = ( 0.35 planes/min ) × 4.8 min
N = 1.68 planes ≈ 2 planes
Therefore, Number of planes on the runway or waiting to take off is approximately 2
