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Problem-Solving and Data AnalysisEasyMeaning of a constant in a draining model

Problem-Solving and Data Analysis practice question

The equation y = 40 − 2x models the number of litres y of water left in a tank x hours after it starts draining. What does the number 40 represent?

  1. A. The number of litres in the tank when draining starts.Correct
  2. B. The number of hours until the tank is empty.
  3. C. The number of litres drained each hour.
  4. D. The number of litres left after 2 hours.

Answer: A. The number of litres in the tank when draining starts.

At x = 0, y = 40.

Why the other answers are wrong

B. The number of hours until the tank is empty.
The tank empties after 20 hours.
C. The number of litres drained each hour.
2 litres drain each hour.
D. The number of litres left after 2 hours.
After 2 hours, 36 litres are left.

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