<PRE><B>Question 4262</B>
Here, you are given the height (h) and are asked to find the time (t) at which this height will occur.  The problem is solved by substituting the given value of h (120 meters) into the formula, and solving for t.

120 = 50t - 5t^2  Rewrite this into standard quadratic equation form:

-5t^2 + 50t - 120 = 0 Divide through by -5 to facilitate the calculation.

t^2 - 10t + 24 = 0   Solve this quadratic equation by factoring.

(t - 12)(t + 2) = 0  Apply the zero products principle.

t - 12 = 0,  t = 12
t + 2 = 0,   t = -2  Discard this solution as a negative value for time is not meaningful.

Answer: 12 seconds.
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