Return on investment is calculated by dividing A) controllable margin by sales. B) contribution margin by sales. C) contribution margin by average operating assets. D) controllable margin by average operating assets. Solution D) Controllable Margin by average operating assets. Reason: Return on Investment measures the performance of the investment made in Assets and return generated by that investment. It is calculated by dividing the Controllable margin by average operating assets. (Opening Assets + Closing Assets / 2) .