# Question Video: The Belonging of a Number of Items to a Certain Set

Decide whether the answer to the following question belongs to ℕ: How many pages are there in a book?

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### Video Transcript

Decide whether the answer to the following question belongs to ℕ: How many pages are there in a book?

ℕ is the set of natural numbers, commonly known as the counting numbers. So the natural numbers include one, two, three, four, five, six, seven, eight, nine, 10, all the way till positive infinity. So when we have to count things, we begin with one because there will be one thing to count and then two, then three, four, five, and so on.

So does the answer to this question belong to the natural numbers? It says how many pages are there in a book. That’s what it’s asking. So the answer would have to be a number. Well, can we have zero pages in a book? No. Could we have a negative number of pages in a book? No. Could we have a half of a page in a book? No.

The number of pages possible in a book will have to begin with one or have to be at least one page. And if there’ll be more than that, there’ll be two pages. And if there’ll be more than that, there’ll be three pages and so on. Therefore, our final answer will be that it does belong to the natural numbers.