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AlgebraEasyDepth function for a leaking pool

Algebra practice question

A pool is 150 centimetres deep and loses 2 centimetres of depth each day. Which function gives the depth d, in centimetres, after t days?

  1. A. d = 150 − 2tCorrect
  2. B. d = 150 + 2t
  3. C. d = 2t − 150
  4. D. d = 150t − 2

Answer: A. d = 150 − 2t

Start at 150 and subtract 2 for each day.

Why the other answers are wrong

B. d = 150 + 2t
This deepens the pool.
C. d = 2t − 150
This is negative for small t.
D. d = 150t − 2
This multiplies the depth by the days.

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