Orange Food with Story Problem

One of RantWoman's exercises in shopping with flair, pizazz, and panache is the grab a meal to make on the run. This means shop enroute to the potluck and rely on one's friends to have ways to steam asparagus or a recent RantWoman / RantMom delight, grab ingredients for a meal and take to RantMom's to prepare.

Here is the grocery list that resulted from a recent fixation on orange food:

Baked yam slices

Carrots, potatoes, commercial soup

sliced cheese

bakes in 10 minutes bread

A bag of tangelos

2 gourmet cookies

RantWoman, singularly, needed to shop while enroute to a No New Youth Jail event. Toting one's groceries to a protest is seriously hardcore. That's right, nerd and proud.

Then there is the story problem with the soup:

RantWoman could have just gotten the creamy tomato soup in a box.

Instead RantWoman, partly for budget reasons opted for one of the commercial brands that has a zillion times more sodium / serving than any sane person should eat. The story problem / linguistic numbers representation part:

If you add enough vegetables to triple the volume of the soup (assume the vegetables are 0% sodium)  but the resulting pot of soup winds up being 3 servings, just 3 larger servings than the package nutrition info. By what percentage does adding more vegetables cut the actual sodium / serving?