Karen can read 10 pages and complete 15 math problems in 30 minutes how long will it take her to do her homework if she has 30 pages to read and 45 math problems to complete?
Karen can read 10 pages in 30 minutes, so she can read 30 pages in (30/10) * 30 = <<30/10*30=90>>90 minutes.
Similarly, she can complete 15 math problems in 30 minutes, so she can complete 45 math problems in (45/15) * 30 = <<45/15*30=90>>90 minutes.
Therefore, it will take her 90 minutes to do her homework. Answer: \boxed{90}.