Answer: B) 6 minutes
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Step-by-step explanation:
Let's find the slope of the table. This will tell us the rate of change.
m = slope
m = (y2-y1)/(x2-x1)
m = (25250 - 26375)/(2 - 1) .... I used the first two rows
m = -1125/1
m = -1125
The slope of -1125 means the plane's altitude is decreasing at a rate of 1125 feet per minute. This is the descent speed.
Since we're told the initial altitude was 27500 ft, this means b = 27500
This means y = mx+b turns into y = -1125x+27500
x is the number of minutes and y is the altitude at time x
As a way to check this, plug in various x values of the table. You should get corresponding y values that match the table. I'll let you do this part.
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Now plug in y = 16250 and solve for x
y = -1125x+27500
16250 = -1125x+27500
-1125x+27500 = 16250
-1125x = 16250-27500
-1125x = -11250
x = -11250/(-1125)
x = 10
It takes 10 minutes after the descent period has started, for the pilot to get to 16,250 ft.
Since the pilot was contacted at the x = 4 minute mark, this means 10-4 = 6 minutes is the duration needed for the pilot to go from 23,000 ft to 16,250 ft.