What new mAs will maintain radiographic density when changing from a 200 speed to a 400 fill-screen system using 20 mAs?

Question

Quizplus · Accepted Answer

When changing from a 200 speed to a 400 speed film-screen system, the amount of radiation needed is halved because the 400 speed system is twice as sensitive as the 200 speed system. Therefore, to maintain radiographic density, you would need to reduce the original mAs (20 mAs) by half, which results in 10 mAs.

What New MAs Will Maintain Radiographic Density When Changing from a 200