Problem-Solving and Data AnalysisMediumInterpreting the slope of a decreasing model
Problem-Solving and Data Analysis practice question
The amount of water y, in litres, in a garden tank t days after a rainstorm is modelled by y = 250 − 12t. Which of the following is the best interpretation of the number 12 in this model?
- A. The tank loses 12 litres of water each day.Correct
- B. The tank held 12 litres right after the storm.
- C. The tank is empty after 12 days.
- D. The tank gains 12 litres each day.
Answer: A. The tank loses 12 litres of water each day.
The slope −12 means y falls by 12 litres per day.
Why the other answers are wrong
- B. The tank held 12 litres right after the storm.
- The starting amount is the intercept, 250.
- C. The tank is empty after 12 days.
- The tank empties when 250 − 12t = 0, at about 21 days.
- D. The tank gains 12 litres each day.
- The slope is negative: a loss, not a gain.
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