<PRE><B>Question 95519</B>
When it strikes the ground the height = zero.
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 48 + 32t - 16t^2 = 0
16t^2-32t-48 = 0
Divide thru by 16 to get:
t^2-2t-3=0
Factor to get:
(t-3)(t+1)
Positive answer:
t = 3 seconds
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The arrow will be on the ground 3 seconds after it was shot up.
Cheers,
Stan H. 
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