"Faster! She is waiting for us."
In this case either 在 or 着 could be used, but you certainly dont need both. 着 Is kind of like -ing, but not strictly. It means that the subject is in an ongoing state (of being something). 在 Before a verb means an action is currently happening. The verb 'wait' is a strange case, because it is both a sort of action, but also a passive state, so im not totally positive which is more correct. But i know you dont need both, like duo thinks.
As i understand it, using both emphasizes it more, but I'm not sure how common or uncommon it is.
Why is it only correct with both "在" and "着"? I left out the "着" and was marked wrong. It would be nice if it told you the rule you're breaking when marking these wrong.
Would it be acceptable to drop the 在 and just have 等着 instead of 在等着? Is there a significant change in meaning?
This is another question that requires an erhua answer (with "一點兒" instead of "一點"); "快一點！她在等著我們。" is rejected.
I've said it without the 在 in normal conversation, is it actually needed?
I would also like perhaps a better explanation of the usage of 在 here. 着 makes a lot more sense to me here.
Looks like the 着 have similiar function of the verb+ing in english. Implies the action is still active