Answer:
1 plane
Step-by-step explanation:
Let's suppose the number of planes waiting or on the runway " P "
the number of planes taking off per hour '
'
the time for waiting and the runway
so:
P =
x 
= 18 airplanes per hour
we know that 1 min = 60s
36s = 36/60 = 0.6 min
Also, 3 min and 30 s = 3 + 30/60 = 3.5 min
Next to find the time for waiting and the runway
∴
= 0.6 + 3.5 = 4.1 min/60 (converting into hour)
= 0.068 hour
P = 18x0.068 = 1.23
therefore, there is 1 plane either on the runway or waiting to take off
So, there is 1 plane either on the runway or waiting to take off
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