If it costs 2.55 dollars to rent 3 books at the library, how much would cost to rent 51 books?

3 books = $2.55

51 books = x $

(3 books / $2.55) = (51 books / x)

then solve for x (aka cross multiply and divide)

To find out how much it would cost to rent 51 books, we can set up a proportion using the given information.

We know that the cost of renting 3 books is $2.55. Let's label this as the first ratio:

3 books / $2.55

To find the cost of 51 books, we set up the same ratio:

51 books / x

Now we just need to set up a proportion:

3 / $2.55 = 51 / x

To solve this proportion, we can use cross multiplication:

3x = 51 * $2.55

Now, we multiply 51 by $2.55:

3x = $130.05

To isolate x, the unknown value representing the cost of renting 51 books, we divide both sides of the equation by 3:

x = $130.05 / 3

Evaluating this expression, we can find the cost of renting 51 books:

x ≈ $43.35

Therefore, it would cost approximately $43.35 to rent 51 books at the library.