Tips & Tricks Let the cost price be 100x ⇒ Selling price = cost price × (100 + profit)% ⇒ Selling price = 100x × 122.5% ⇒ Selling price = 122.5x ⇒ The ratio of the cost price to the selling price = 100x : 122.5x = 40 : 49 ∴ The ratio of the cost price to the selling price is 40 : 49.