Answer
$68$ft
Work Step by Step
As we are given that $h(t)=-16t^2+48t+32$
Here, $a=-16,b=48,c=32$
and $a =-16 \lt 0$ and this shows a maximum value at the point $h=\dfrac{-b}{2a}=-\dfrac{(48)}{2(-16)}=1.5$
Consider: $k=h(1.5)=-16(1.5)^2+48(1.5)+32$
Thus, the maximum height or value of the stone reaches at: $k= 68$ft