Which masses (weights) must be applied in a ratio for the calculation of the maximum permissible towed load behind a truck (continuous brake system)?

The correct ratio used for calculating the maximum permissible towed load behind a truck with a continuous brake system is the ratio of the permissible total mass (allowed maximum weight) of the truck to the actual mass (current weight) of the trailer. This means you compare what the truck is allowed to weigh at most (its permissible total mass) with the actual weight of the trailer being towed.

This ratio is important because the permissible total mass of the truck represents the legal limit for safe and allowed operation, while the actual mass of the trailer tells you how heavy the load really is. Using these two values ensures that the towing arrangement stays within legal and safe limits.

The other options are not correct because they either mix actual and permissible masses in the wrong way or compare total permissible masses of both vehicles, which does not reflect the actual loading conditions. Understanding this helps ensure that the truck and trailer combination is properly loaded, stable, and complies with regulations.