There are 15 books. Five books fit on one shelf. How many shelves are needed?
Here, we have a word problem. It’s based on real life, and it doesn’t tell us what we need to do to find the answer. So, let’s read it again more carefully and think about what operation we need to use. Firstly, we’re told a total amount of books. There are 15 books. Let’s use this bar to represent our 15 books.
The next sentence in our problem talks about splitting up our 15 books. It tells us that five books fit on one shelf. So clearly, we’re going to be taking our 15 books and splitting them up onto shelves. Let’s let this part here represent five books that we’ve put on a shelf. And the question asks us, how many shelves are needed?
We have 15 books to start with, and we can only fit five books on a shelf. So, we need to find the number of fives that there are in 15. In other words, what is 15 divided by five. This is a division question. Now, one way to find out how many groups of five there are in 15 is to use a multiplication fact we already know to help.
Let’s remind ourselves of our five times table facts by starting at zero and skip counting in fives. One times five is five. Two fives are 10. And three fives are 15. Let’s write out that multiplication fact. Three multiplied by five equals 15. We can use this number fact and read it backwards as a division. 15 divided by five equals three.
In other words, we can make three groups of five from 15. And so, if there are 15 books and five books fit on a shelf, then the number of shelves that are needed is three. 15 divided by five equals three.