Question

After reading $\frac{7}{9}$ of a book, 40 pages are left. How many pages are there in the book?

Answer 1

Ratio of the read book = $\frac{7}{9}$
Ratio of the unread book = $1-\frac{7}{9}$

$=\frac{2}{9}$
Let x be the total number of pages in the book.

Thus, we have:

$$\begin{gathered} \frac{2}{9}\times x=40 \\ \Rightarrow x=40÷\frac{2}{9} \end{gathered}$$

$$\begin{gathered} =40\times \frac{9}{2} \\ =\frac{40}{1}\times \frac{9}{2} \\ =\frac{40\times 9}{1\times 2} \\ =\frac{360}{2} \\ =180 \end{gathered}$$

Hence, the total number of pages in the book is 180.