Final answer:
The constant gross-margin percentage method allocates joint costs by deducting the gross margin and separable costs from the final sales value of a product.
Step-by-step explanation:
The constant gross-margin percentage method allocates joint costs by calculating a gross margin for each product and deducting it, along with separable costs, from the final sales value of the product. The remaining amount after deductions represents the joint cost allocation for that product. This method bases the allocation on the gross margin and sales value of each product, rather than on physical volume measures.