6
advanced-math

A stone is dropped from a bridge 144 ft high. h(t)=−16t2+144h(t) = -16t^2 + 144. How long until it hits the water?

A

3 seconds

B

9 seconds

C

4.5 seconds

D

12 seconds

Correct Answer: A

Choice A is the correct answer. Set h(t)=0h(t) = 0.

  1. −16t2+144=0-16t^2 + 144 = 0.
  2. 16t2=14416t^2 = 144.
  3. t2=9t^2 = 9.
  4. t=3t = 3 seconds.

Choice B is incorrect. Choice C is incorrect. Choice D is incorrect.

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Set 17: Quadratic Equations and Functions 17