I think using percentages to plan the purchase of food in a ratio is better than using ratios. They are almost the same things, but I think using percentages would be easier. My reason for that is because it is easy to read. Everybody knows that any percent is out of 100, so basically, its like any portion out of a 100. That's pretty easy to realize and read. For example, if someone said they would like to order 40% of the platter of fried rice, they basically would basically almost half of it.
Another reason why it would be right to use percentages to plan the purchase of food because it isn't difficult math. Who would want to go through a lot of stress just to plan for food? Percentages are divided into correct parts, and I think it would be perfect for food because there is a lot of seperating and sectioning.