#### Answer

time taken $\approx$ 5.86 seconds

#### Work Step by Step

$Change in height = H-h = ut + \frac{1}{2}at^{2}$
Initial velocity (u) for free fall=0
Final height (H) is 0
Initial height (h) is 550
The time taken to reach the ground is given as t
Plug in values
$0= 550 + 0*t -16t^{2}$
$550 =16t^{2}$
$t^{2}=550/16$
$t=\sqrt {550/16}$$\approx$ 5.86 seconds