Question 745513
{{{ s(t)  = -16t^2 + 150t + 2 }}}
{{{ s(t) }}} is the height of the rocket from the ground
If you want the height to be {{{ 300 }}} ft, then
{{{ s(t) = 300 }}}
{{{ 300  = -16t^2 + 150t + 2 }}}
{{{ -16t^2 + 150t - 298 = 0 }}}
Divide through by {{{ 2 }}}
{{{ -8t^2 + 75t - 149 = 0 }}}
Use quadratic wquation
{{{ t = (-b +- sqrt( b^2 - 4*a*c )) / (2*a) }}}
{{{ a = -8 }}}
{{{ b = 75 }}}
{{{ c = -149 }}}
{{{ t = (-75 +- sqrt( 75^2 - 4*(-8)*(-149) )) / (2*(-8)) }}}
{{{ t = (-75 +- sqrt( 5625 - 4768 )) / (-16) }}}
{{{ t = (-75 +- sqrt( 857 )) / (-16) }}}
{{{ t = (-75 + 29.275) / (-16) }}}
{{{ t = -45.725/(-16) }}}
{{{ t = 2.858 }}} sec
In 2.858 sec the height of the rocket will be 300 ft
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I have to run now- check my math. The method 
should be OK