Stacking pages

[bigbill]

Ann was collating pages of a report.She had a stack of each page, the exact number ,and was building a separate stack of complete sets. She had taken just as many mins as there are stacks here. The stacks now have the same no of sheets. It will take 90 minutes to finish if she carries on @ the same speed. How many pages in each complete set ? I can do a lot of time/work problems, this has me badly stumped. Thanks in advance.

 

[HallsofIvy]

I can see no way to answer this given only that "she had taken just as many mins as there are stacks here". If it will take her 90 minutes to finish, at that same rate, then she has 90 stacks. But there is no way of knowing how many sheets of paper there are in each stack.