Question

The cost of a book is three times the cost of a notebook. Keshav bought five notebooks and five books for $₹600$. Find the price of the notebook and book.

Answer 1

Find the cost of the notebook and book:

Let the cost of a notebook be $₹x$.

$\therefore$The cost of a book $=₹3x$

Now, the cost of five notebooks and five books $=₹600$

$\therefore$ $$\begin{gathered} 5x+5\left(3x\right)=600 \\ 5x+15x=600 \\ 20x=600 \\ x=30 \end{gathered}$$

$$\begin{gathered} \therefore x=30 \\ 3x=90 \end{gathered}$$

Hence, the cost of a notebook is $₹30$ and the cost of a book is $₹90$.