Answer:
0.9043secs and 0.3456secs
Explanation:
Given the height of an overhand volleyball modeled as h=-16t^2+20t+6.
If the height is 11feet, then;
11 = -16t^2+20t+6.
-16t^2+20t+6 - 11 = 0
-16t^2+20t-5 = 0
Multiply thriugh by -1
16t^2-20t+5 = 0
Factorize
t = 20±√20²-4(16)(5)/2(16)
t = 20 ±√400-320/32
t = 20 ±√80/32
t = 20 ±4√5/32
t = 20±8.94/32
t = 28.94/32 and 11.06/32
t = 0.9043 and 0.3456
Hence the required time are 0.9043secs and 0.3456secs