Question 1090094
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To find the time under the question, solve the equation

{{{-16*t^2 + 200}}} = 0,   or, which is the same,

{{{16*t^2}}} = 200  ====>  {{{t^2}}} = {{{200/16}}} = 12.5  ====>  t = {{{sqrt(12.5)}}} = 3.54 seconds  (approximately).
</pre>

Solved.