Advanced MathVery hardInput from an output of a quadratic in context
Advanced Math practice question
A rocket's height, in metres, t seconds after launch is h(t) = −5t² + 40t. At what time t, after reaching its peak, is the rocket at a height of 60 metres?
Answer: 6
−5t² + 40t = 60 gives t² − 8t + 12 = (t − 2)(t − 6) = 0. The peak is at t = 4, so the time after the peak is t = 6.
Common wrong answers
- If you answered 2
- 2 is when the rocket passes 60 m on the way UP, before the peak.
- If you answered 4
- 4 is the time of the peak itself.
- If you answered 8
- 8 is when the rocket lands (h = 0).
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