How can you
use dimensional analysis to convert between measurement
systems?

Firstly, you should find 10% of 9, which is 0.9 You've then got to multiply this by 5.5, as you've got 55 books. 0.9x5.5= 4.95 Therefore, as you cannot have .95 of a books, this has to be rounded to 5. Therefore, the library has 5 books out on the topic. Hope this helps :)