Answer:
30cm
Step-by-step explanation:
Assuming that the thickness of the books is 2cm (This is a reasonable assumption, as books are almost always longer and wider than they are thick, and assuming that the books are stacked flat on top of one another, faces up or down, and not sideways, the question becomes 'What is the height of 15 books stacked on top of one another, if each book is 2cm thick?' The answer to this question is 15*2 or 30.
