Explanation:
0,4 ft
It can be convinient to let a spreedsheet compute the values for you
Here we have written an expiliclit formula for the height of the 9th bounce
H= 5.5 x 0.64'(n-1)
We have written the formuka this way beacause we are given the height of the firrrst bounce not the satrting height so as you see each bounce multiples the height by a factor of 0,64 then the 7th bounce will be
H= 5.5 x 0.64'6 = 0.378 = 0,4 feet
Hope it helps