Question 356085
The volume of a hemisphere (half-sphere) is half of this volume: 



The key is knowing that hemi- (meaning half) sphere is just half of a whole sphere.


Compute the full volume using:
V = 4/3 π r^3



Then divide by 2 or do it from the beginning:


V(hemi) = 2/3 π r^3



Can you take it from here?