Final answer:
The retail mark-up percentage on the antique clocks is calculated by dividing the difference between the selling price and cost price by the cost price, then multiplying by 100%. This results in a mark-up of 118%.
Step-by-step explanation:
To calculate the percentage mark-up, we use the formula:
Percentage Mark-Up = ((Selling Price - Cost Price) / Cost Price) × 100%
From the question, the Selling Price (SP) is $545 and the Cost Price (CP) is $250.
Therefore, let's calculate the mark-up percentage:
Mark-Up = $545 - $250
Mark-Up = $295
Percentage Mark-Up = ($295 / $250) × 100%
Percentage Mark-Up = (1.18) × 100%
Percentage Mark-Up = 118%
So, the retailer has a 118% mark-up on the antique clocks.