Answer :
The answer is 2.... The 6x4 photo because that's the only one with common factors so there won't be any empty space at the end.
As far as how many... find the area of both and divide:
6x4=24
72x72=5184
5184/24= 216 photos
As far as how many... find the area of both and divide:
6x4=24
72x72=5184
5184/24= 216 photos