5th grade math

I ran across a discussion of what was claimed to be a 5th grade math problem. Can you work it in your head?

A student started reading a book on Monday and read 30 pages. She read one eighth of the book on Tuesday and the remaining quarter of the book on Wednesday. How many pages are there in the book?”

(I supplied the fact that was omitted from the original, that she started on Monday. Otherwise the problem is indeterminate because she could have previously read any number of pages.)