16Hit1600
AlgebraVery hardInterpreting a small negative slope

Algebra practice question

The function T(d) = 15 − 0.0065d models the air temperature T, in degrees Celsius, at a height of d metres above a town. Which of the following is the best interpretation of the number 0.0065 in this context?

  1. A. The temperature decreases by 0.0065 degrees Celsius for each additional metre of height.Correct
  2. B. The temperature at ground level is 0.0065 degrees Celsius.
  3. C. The temperature is 0 degrees Celsius at a height of 0.0065 metres.
  4. D. The temperature increases by 0.0065 degrees Celsius for each additional metre of height.

Answer: A. The temperature decreases by 0.0065 degrees Celsius for each additional metre of height.

The coefficient of d is the change in T per metre, and its sign is negative.

Why the other answers are wrong

B. The temperature at ground level is 0.0065 degrees Celsius.
The ground-level temperature is the constant, 15.
C. The temperature is 0 degrees Celsius at a height of 0.0065 metres.
T = 0 at d = 15/0.0065, about 2,300 metres.
D. The temperature increases by 0.0065 degrees Celsius for each additional metre of height.
The slope is negative, so the temperature falls.

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