The math example posted by Matchmakersmagic is INCORRECT.
You cannot determine the ratio of a combination of foods by adding the ratios.
You must determine the mg amounts of both calcium and phosphorus in the AMOUNT of each food you are combining.
A ratio is a comparison of the amounts of calcium and phosphorus. A food with 30 mg calcium and 15 mg phosphorus would have a ratio of 2:1 but so does a food that has 100 mg calcium and 50 mg phosphorus.
Here is a printable sheet that demonstrates the correct calculation of ratios for combinations of foods.
http://www.gliderkids-diet.com/RatioExample.pdf
I also have an excel spread sheet on my web page that will do the math for you if you really wish to figure out what you are offering. If you are using one of my staple recipes you can include the staple and do the calculation for the entire feeding. (link to the spread sheet is on the right hand side of the page.
http://www.gliderkids-diet.com/Staple-Recipes.html
You do not have to feed 'combinations' of foods and you will probably find it almost impossible to come up with any combinations that actually have that magic number of a 2:1 ratio unless you go overboard with the bok choi and papaya to balance out the other foods you choose.
It is much easier to just limit the very high phosphorus foods like peas and corn to only once or twice a week and include some of the high calcium foods several nights each week and don't sweat the ratios.