7
algebra

A tank contains 100 gallons of water and drains at a rate of 5 gallons per minute. Which equation models the volume VV after tt minutes?

A

V=−5t+100V = -5t + 100

B

V=5t+100V = 5t + 100

C

V=100t−5V = 100t - 5

D

V=−5t−100V = -5t - 100

Correct Answer: A

Choice A is the correct answer. Draining means negative slope.

  1. Rate: Draining 5 gal/min →\rightarrow Slope is −5-5.
  2. Start: 100 gallons →\rightarrow Intercept is +100+100.
  3. Equation: V=−5t+100V = -5t + 100.

💡 Strategic Tip: "Drains", "Falls", "Decreases" always imply a negative slope.

Choice B is incorrect because it implies the tank is filling up. Choice C is incorrect because it swaps rate and start. Choice D is incorrect because it implies negative initial volume.

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Linear Functions Set 83