Calculate KPI

Calculate KPI

Hello.

I have 2 KPI on my board.

For example I have a board with:
 - KPI 1 - Total of balls (10)
 - KPI 2 - Red balls (3)

I need calculates the percentage of red balls refer to total balls

I need the KPI 3 - With result 30%, in this example.

There's a way?

Thank you