Final answer:
To determine the selling price with a 25% profit, the cost price must be multiplied by the factor of 1.25.
Step-by-step explanation:
The question involves determining the factor by which the cost price must be multiplied to find the selling price when a profit of 25% is made. To find this factor, we add the profit percentage to 100% (which represents the original cost price), resulting in 125% or 1.25 as a decimal. Therefore, the cost price must be multiplied by 1.25 to obtain the selling price.