Final answer:
The time required for the projectile to return to earth is approximately 0.3578 seconds.
Step-by-step explanation:
To find the time required for the projectile to return to earth, we need to solve the equation h = -166 + 464t for t when h = 0, since the height of the projectile is 0 when it returns to earth.
0 = -166 + 464t
166 = 464t
t = 166/464
t = 0.3578 seconds
Therefore, the time required for the projectile to return to earth is approximately 0.3578 seconds.