# 15% Rule Equation & Practice - Video Lesson

This lesson is about the fifteen percent KVP rule. It's usually used to control contrast while at the same time maintaining receptor exposure. So here's how the rule works. If we increase KVP by fifteen percent, our mass must decrease by half in order to maintain the same exposure. If KVP decreases by fifteen percent, our mass must increase by double in order to maintain the same exposure. So let's look at a few sample problems and see how this works in practice. So here's question number one. If mass is increased by one hundred percent, which is the same as being doubled, how should KVP be changed in order to maintain the same exposure to the image receptor So our mass is increasing by double. So what does our KVP need to do? This is essentially the definition of the fifteenth percent KVP rule. If our mass is increasing by double, our KVP must decrease by fifteen percent

## Lesson Quiz

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