Ok, I've answered my own question. In the du command form, the "e" at the end is optional — so it could be "wasch" or "wasche," doesn't matter. And "dir" is not there because this is a command to wash some other feet, not their own feet.
So... maybe it's a pedicure salon. Or maybe there's a big pile of feet that need washing. I dunno, Duo.
I had the same question. This appears to be the 2nd person imperative singular: http://conjugueur.reverso.net/conjugaison-allemand-verbe-wasche.html
This depends on the language. In English and German, both uses correspond, and you should translate them directly. The above sentence does not mean "wash your feet", and "wash the feet" sounds as strange in German as it does in English, believe me. It's another 'Duolingo Special' ;-)
In Spanish, which I see you're also learning, they would always say "las piernas" in this context, rather than "tus/sus piernas". In Spanish, you would never refer to your feet as your feet, but always as "the feet". Of course, English and German native speakers routinely get that wrong in Spanish.
Same here (1/1/19). And unfortunately a lot of the comments are addressing this issue, but no moderators have chimed in. It appears all are users just like you and me. Maybe someone is highly qualified, but how are we to know? I'm reporting it. Hopefully we'll find out soon.
I'm going to make a guess anyway that whoever thought up the sentence was THINKING 'wash your feet' and then it occurred to them that a dative possessive is above our Level 10 heads. Otherwise, it's very hard to find a probable scenario for using it. Feet always belong to someone, except when they wash up on beaches in Canada.
One observation, in Spanish you don't say "lava tus piernas", neither "lava las piernas" but "lavate las piernas" or "lavate los pies" (more correct here), so you add "-te" after de verb, indicating it's your feet.
Anyway, in this sentence it could mean that you have to wash the feet to someone else. Sometimes there are strange sentences to translate.
My high school german teacher told us that for imperatives in the informal second-person (when you would normally use du), you omit the "du", remove the "-en" from the infinitive to leave only the stem, and add an exclamation point to the end. So the sentence should read "Wasch die Füße!"
Is this correct? Should I report this question?