Please explain these for me.
After doing a few online-examination that teacher told me to do. I noticed there are questions I don't quite understand.
1. "Is there a bank where I can exchange FOR these pounds for dollars?"
("for" is blank and also is the answer.) which makes me confused. "Exchange for these pounds for dollars???????" is anything wrong with this. (notice that sometime the mistake is that the online-examination itself.)
2. "The landslide delayed the train's departure by a few hours."
"By a few hours" is what I don't understand. Does it have the same meaning as "for a few hours"??

Question

Please explain these for me.
After doing a few online-examination that teacher told me to do. I noticed there are questions I don't quite understand.
1. "Is there a bank where I can exchange FOR these pounds for dollars?"
    ("for" is blank and also is the answer.) which makes me confused. "Exchange for these pounds for dollars???????" is anything wrong with this. (notice that sometime the mistake is that the online-examination itself.)
2. "The landslide delayed the train's departure by a few hours."
   "By a few hours" is what I don't understand. Does it have the same meaning as "for a few hours"??

Answer

1. That does sound weird because you could just take out the blank and it would sound fine.  The only thing I could think of is that you could put a number in there.  For example, "Is there a bank where I can exchange 20 of these pounds for dollars."

2. In this case they mean the same thing.

Answer

Thank you

Answer

You're right. I think there was a mistake on the examination. That "for" shouldn't be there.
By a few hours can mean the same thing as for a few hours. The only difference to my mind is that By a Few Hours gives the impression that the departure had been delayed, but the train in now on the way, and For a Few Hours gives more the impression that the train might still be waiting to depart. However, I think they can be used interchangeably.