Problem:
72 books are packed in 4 cartons of the same size. We need to determine how many cartons are required for 540 books.

Solution:
To solve this problem, we can use a basic proportion or ratio method. We have the following information:

- 72 books are packed in 4 cartons.
- We want to determine how many cartons are required for 540 books.

We can set up the proportion as follows:

72 books / 4 cartons = 540 books / x cartons

Now, we can cross-multiply and solve for x:

72x = 4 * 540
72x = 2160
x = 2160 / 72
x = 30

Therefore, 30 cartons are required for 540 books.

Explanation:
To understand why this proportion works, we need to consider the relationship between the number of books and the number of cartons.

In the given scenario, we can see that 72 books are packed in 4 cartons. This means that each carton holds 72/4 = 18 books.

Now, we want to determine how many cartons are required for 540 books. Since each carton holds 18 books, we can divide 540 by 18 to find the number of cartons needed.

540 books / 18 books per carton = 30 cartons

Therefore, 30 cartons are required for 540 books.

Summary:
To summarize, we can determine the number of cartons required for a given number of books by setting up a proportion. In this case, we found that 30 cartons are needed for 540 books. It is important to understand the relationship between the number of books and the number of cartons to solve this type of problem effectively.

= 72\4=18\540. 30 cartons