At the library, you find 9 books on a certain topic. The librarian tells you that 55% of the books of this topic have been signed out. How many books does the library have on this topic?

20books

Step-by-step explanation:

Let x be the initial number of books on the shelf,

If 55% of the books have been signed out, then 45% (100-55) of the total books would have been left on the shelf i.e 45%of x

Since I found 9 books on the topic, we will equate 45%of x to 9 to get the initial number of books on the topic that is;

45x/100 = 9

45x = 900

x = 900/45

x = 20

This shows that the library has 20books on the topic

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