How long should I bake a whole sweet potato in the oven for versus an 'ordinary' potato of the same size?
There are many varieties of sweet potato that have quite different cooking times
Many cultures have diverse ideas of what "done" is, some have it quite firm, some have it mushy
In general for your average sized sweet potato you should only need 50% to 75% of potato cooking time using the same method and weight
It depends on what your preference is or what you are cooking. If I want a firmer texture, roasted or sliced I shoot for 30 minutes give or take. If I want a soft texture, mashed potatoes or soup then I will cook them around 45 minutes. Of course it will always depend on the width of the sweet potato. If I am cooking both potatoes and sweet potatoes, I will fist put the regular potatoes in the oven first, then 20 min later add the sweet potato. To test, pierce with a fork not a knife.