Question

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

Answer 1

To find the total number of books on a topic when 9 are available and 55% are signed out, set up a proportion and solve for 'x.' The calculation reveals there are a total of 20 books available on the topic.

Step-by-step explanation:

The student is asking how many books on a certain topic the library has available if 9 books are found and 55% of all the books on that topic have been signed out. To find the total number of books on the topic, we need to understand that the 9 books on the shelf represent 45% of the total books (100% - 55% = 45%). We can set up a proportion where 9 books is to 45% as the total number of books (let's call it 'x') is to 100% (the whole set of books on the topic).

Setting up the proportion, we have:

9 / 45% = x / 100%

To solve for 'x,' we cross-multiply and divide as follows:

9 * 100 = x * 45

900 = 45x

Now we divide both sides of the equation by 45 to find 'x':

x = 900 / 45

x = 20

Therefore, the library has a total of 20 books available on the topic.

Answer 2

Multiply 9 books by 55% by doing

9 x .55 = 4.95

We can't have 4.95 books, though so it rounds down to 4 because you can't just add another .05.