Ritu bought a saree for ₹60x and sold it for ₹(500 + 4x) at a loss of x%. Find the cost price.

Cost price of saree = ₹60x

Selling price of saree = ₹(500 + 4x)

Loss perecent = x%

Loss percent = $\dfrac{\text{Cost price - Selling price}}{\text{Cost price}} \times 100$

$\therefore \dfrac{60x - (500 + 4x)}{60x} \times 100 = x \\[1em] \Rightarrow \dfrac{60x - 500 - 4x}{60x} \times 100 = x \\[1em] \Rightarrow 100(56x - 500) = 60x^2 \\[1em] \Rightarrow 5600x - 50000 = 60x^2 \\[1em] \Rightarrow 60x^2 - 5600x + 50000 = 0 \\[1em] \Rightarrow 20(3x^2 - 280x + 2500) = 0 \\[1em] \Rightarrow 3x^2 - 280x + 2500 = 0 \\[1em] \Rightarrow 3x^2 - 250x - 30x + 2500 = 0 \\[1em] \Rightarrow x(3x - 250) - 10(3x - 250) = 0 \\[1em] \Rightarrow (x - 10)(3x - 250) = 0 \\[1em] \Rightarrow x - 10 = 0 \text{ or } 3x - 250 = 0 \\[1em] x = 10 \text{ or } x = \dfrac{250}{3} \\[1em]$

x ≠ $\dfrac{250}{3}$ as this value will make the selling price in fraction.

∴ x = 10 , Cost price = 60x = 600

The cost price of saree is ₹600.