Advanced MathHardTime at which a projectile is highest
Advanced Math practice question
The height of a rocket t seconds after launch is modelled by h(t) = −5t² + 30t. At what time is the rocket at its maximum height?
- A. 3 secondsCorrect
- B. 6 seconds
- C. 45 seconds
- D. 30 seconds
Answer: A. 3 seconds
The maximum of a downward parabola is at t = −b/(2a) = −30/(−10) = 3.
Why the other answers are wrong
- B. 6 seconds
- 6 seconds is when the rocket returns to the ground (h = 0).
- C. 45 seconds
- 45 is the maximum HEIGHT (h(3)), not the time.
- D. 30 seconds
- 30 is the coefficient b.
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