Asked by Sarah

A ball is thrown vertically upward from the ground. Its distance in feet from the ground in t seconds is s=-16t^2+208t. After how many seconds will the ball be 640 feet from the ground?
Answered by Reiny
solve -16t^2+208t = 640
t^2 - 13t + 40 = 0
(t-5)(t-8) = 0

t = .....

interpret this result
Answered by Damon
Quite a throw.
Answered by Reiny
And that wasn't even the maximum height !!!