Create new column with ratio based on values in one column and filter on other column

[Arual123]

Hi there, 

I am trying to create a new column "Ratio" which calculates the ratio of the quantities sold (#) in the product groups (A/B) in a specific calendar week: # product A/ (# product A + # product B)

Product group	Calendar Week	Quantities sold (#)	Ratio
A	1	12	Ratio (week 1)= 12/(12+8)
B	1	8	Ratio (week 1)= 12/(12+8)
A	2	14	Ratio (week 2)= 14/(14+7)
B	2	7	Ratio (week 2)= 14/(14+7)

Thank you in advance!

[wdx223_Daniel · Accepted solution]

@Arual123  try this in a calculated column

and this in a visual