There are several information's already given in the question. Based on those given information's the answer can be easily deduced.
First angle of depression = 18°33'
= [18 + (33/60)] degree
= 18.55 degrees
Second angle of depression = 51°33'
= [51 + (33/60)] degrees
= 51.55 degrees
Height of the lighthouse = 200 feet
Then
Distance traveled by the boat from when it
was first noticed until it stopped = (200/tan 18.55) - (200/tan 51.55)
= (200/0.3356) - (200/1.2594)
= 594.95 - 158.81
= 436.14 feet
I hope the procedure is clear enough for you to understand.
The molecules of the perfume diffuse through the room at a certain critical concentration and later are detected by our noses.
