Three sisters, aged 81, 83 and 85, live together

One night the 85 year old draws abath for herself. As she sticks her foot in, she pauses. She yells to her sisters downstairs, "Was I getting in or out of the bath?" The 83 year old shouts back loudly, "I don't know. Let me come up there and see." She begins walking up the stairs, but then pauses . She yells to her sisters "Was I going up the stairs or down?" The 81 year old is sitting in the living room, enjoying some tea. She listens to her sisters, shakes her head and mutters to herself, "Isure hope I never get that forgetful. Knock on wood." She then turns and shouts, "I'll come up there and help both of you as soon as I see who's knocking at the door."