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AlgebraMediumInterpreting the y-intercept of a decreasing line

Algebra practice question

The function d(t) = 500 − 20t gives the distance, in metres, between a walker and a gate t seconds after the walker starts toward it. Which of the following is the best interpretation of the number 500?

  1. A. The walker starts 500 metres from the gate.Correct
  2. B. The walker reaches the gate after 500 seconds.
  3. C. The walker walks 500 metres per second.
  4. D. The walker is 500 metres past the gate after 20 seconds.

Answer: A. The walker starts 500 metres from the gate.

d(0) = 500: the starting distance.

Why the other answers are wrong

B. The walker reaches the gate after 500 seconds.
The gate is reached when 500 − 20t = 0, at t = 25.
C. The walker walks 500 metres per second.
The speed is 20 metres per second.
D. The walker is 500 metres past the gate after 20 seconds.
After 20 seconds the distance is 100.

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