Ignorance is not having knowledge, you can be both stupid and knowledgable or intelligent and ignorant. Not knowing how to wash your clothes is being ignorant, not being able to figure out how to wash your clothes is being stupid.

EDIT: Not to mention that someone can be stupid in one area and insanely intelligent in another. It’s not a direct personality trait, although people will probably categorize other people based on the categories in which they are one or the other.