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### Question

Each book of a shelf has as many pages as is the total number of books in that shelf. If there are 169 pages in all, how many books are there?

**A**

13.

**B**

16.

**C**

24.

**D**

9.

**Soln.**

**Ans: a**

Let the number of books = n. So pages in one book are also n, and therefore, pages in n books = $n^2$. We have been given $n^2 = 169$, which gives n = 13.