How many pictures can a 512mb memory card hold in a 6 megapix camera?

A 512 MB card can hold more than 1500 images depending on the quality of the images. Eg., If you have taken pics in macro mode or with "super fine" mode, it will occupy more space on the memory card and "fine mode" will take little less space and so on......so it entirely depends on the quality & size of the images present on the card.