Question

A jet plane is descending at a rate of 200 feet per second from an altitude of 36000 feet let x represent the number of seconds of descent and y represent the jet plane’s altitude in feet.

Which expression represents this situation?

A. y = 200x - 36000

B. y = 200x + 36000

C. y = -200x - 36000

D. y = -200x + 36000

Answer 1

Rate of descend = 200 ft/sec

In x second, the plane will have descended by 200*x ft = 200x ft
The altitude of the plane, y after x seconds will be 36000 - 200x. That is,

y= 36000-200x = -200x + 36000.

Therefore, the correct expression representing this situation is D.

Answer 2

Jane's plane will be modeled using linear equation given by:
y=ax+b
where:
a=slope=rate
b=y-intercept or initial valuegiven:
from the question
a=200 ft per second
b=36000 ft
thus the expression representing the situation will be:
y=200x+36000
where x is time in seconds
thus the answer is:
B. y = 200x + 36000