Can I calculate an overall rating if my Competency and Performance have different scales ?

Summary

Can I calculate an overall rating if my Competency and Performance have different scales ?

Content

I have a requirement as follows: 

Goals section - calcluate section rating using scale A - numeric rating 1 to 4 == Section weight is 60% 

Competencies section - calculate section rating using scale B - numeric rating 1 to 4 (a copy of scale A but with different descriptions)== Section weight is 40% 

Overall rating -- I want to calculate an overall rating that includes both Goals and Competencies and their appropriate section weightings however the system only seems to calculate the overall correctly if both sections have the same scale (scale A )