Question 490175
{{{h = vt-16t^2}}} Find t when h = 0 and v = 192.
{{{0 = 192t-16t^2}}} Factor out {{{16t}}}.
{{{0 = 16t(12-t)}}} Apply the "zero product" rule.
{{{16t = 0}}} or {{{12-t = 0}}}
If {{{16t = 0}}} then {{{t = o}}} This the initial condition when the flare is first launched.
If {{{12-t = 0}}} then {{{t = 12}}} This is the time when the flare returns to the sea (height = 0)
The answer is 12 seconds.