Weighted Average of RTY

I was ultimately able to determine the right function.  You need to pre-calculate the table then group by and calculate.  That will ensure the correct order of operations.

RTY Summary = 

var opSummary = 
    SUMMARIZE(
        FTT
        ,[LINE],[OPERATIONNAME],[DATE],[Key Station]
        ,"FPY",DIVIDE(SUMX(FTT,[PASS]),SUMX(FTT,[TOTAL]),0)
        ,"TOTAL",sumx(ftt,[TOTAL])
        ,"KEY_TOTAL",sumx(FILTER(ftt,[Key Station]=True),[TOTAL])
    )

var lineSummary = 
    GROUPBY(opSummary,[LINE],[DATE]
        ,"RTY",PRODUCTX(CURRENTGROUP(),[FPY])
        ,"LINE_TOTAL",SUMX(CURRENTGROUP(),[KEY_TOTAL])
)

return 

CALCULATE(
    DIVIDE(
        SUMX(lineSummary,[RTY]*[LINE_TOTAL]),
        SUMX(lineSummary,[LINE_TOTAL])
    )
)