Getting col % from a base size

Question

I'm trying to get an output for a multi-response table in col%. I can get a % from column total but not from a fixed based. How do I do it? For example

Past week used (Seg A, Seg B, Seg C) = Olive Oil: 80, 100, 150 Sunflower Oil: 35, 95, 105 Coconut Oil: 109, 209, 15

Segment sizes A=120, B=250, C=165

I need col% by each segment

So Seg A should be calculated as Olive Oil= 80/120; Sunflower Oil=35/120 & Coconut Oil=109/120

Similarly for Seg B & Seg C.

I'm using tidyr and dplyr to generate my outputs.

Any advice will be much appreciated.