If the price of a book is reduced by ₹5, a person can buy 4 more books for ₹600.

Solution:

Let the original price of the book be ₹x.

$\therefore$ Number of books bought at original price for ₹ $600=\frac{600}{x}$

If the price of a book is reduced by ₹5, then the new price of the book is ₹(x − 5).

$\therefore$ Number of books bought at reduced price for ₹ $600=\frac{600}{x-5}$

According to the given condition,

$\frac{600}{x-5}-\frac{600}{x}=4$

$\Rightarrow \frac{600 x-600 x+3000}{x(x-5)}=4$

$\Rightarrow \frac{3000}{x^{2}-5 x}=4$

$\Rightarrow x^{2}-5 x=750$

$\Rightarrow x^{2}-5 x-750=0$

$\Rightarrow x^{2}-30 x+25 x-750=0$

$\Rightarrow x(x-30)+25(x-30)=0$

$\Rightarrow(x-30)(x+25)=0$

$\Rightarrow x-30=0$ or $x+25=0$

$\Rightarrow x=30$ or $x=-25$

∴ x = 30               (Price cannot be negative)

Hence, the original price of the book is ₹30.