Explicit

interface IEnglishDimensions
{
    float Length();
    float Width();
}
interface IMetricDimensions
{
    float Length();
    float Width();
}

class Box : IEnglishDimensions, IMetricDimensions
{
    float lengthInches;
    float widthInches;

    public Box(float lengthInches, float widthInches)
    {
        this.lengthInches = lengthInches;
        this.widthInches = widthInches;
    }
    float IEnglishDimensions.Length() => lengthInches;
    float IEnglishDimensions.Width() => widthInches;
    float IMetricDimensions.Length() => lengthInches * 2.54f;
    float IMetricDimensions.Width() => widthInches * 2.54f;

    static void Main()
    {      
        Box box1 = new Box(30.0f, 20.0f);
        IEnglishDimensions eDimensions = box1;
        IMetricDimensions mDimensions = box1;
        System.Console.WriteLine("Length(in): {0}", eDimensions.Length());
        System.Console.WriteLine("Width (in): {0}", eDimensions.Width());
        System.Console.WriteLine("Length(cm): {0}", mDimensions.Length());
        System.Console.WriteLine("Width (cm): {0}", mDimensions.Width());
    }
}