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WAEC Further Mathematics 2010 Question 33

Question 33

Differentiation

A stone is thrown vertically upwards and its height at any time t seconds is h = 45t − 9t2. Find the maximum height reached.

  1. A.45.25m
  2. B.45.50m
  3. C.56.00m
  4. D.56.25m
Show the answer and explanation

Answer: D (56.25m)

Explanation

dh/dt = 45 − 18t = 0 at t = 2.5 s. h = 45(2.5) − 9(2.5)2 = 112.5 − 56.25 = 56.25 m.