I've gone into a few interviews for supposedly senior positions where I was asked to complete tasks that seem utterly simplistic to me. I sometimes walk out of the interview feeling like I've not been given the opportunity to demonstrate the depth of my knowledge. Can anyone offer advice on what you might do in this situation?
I would suggest giving a couple of solutions, explaining the pros and cons of each. This gives you the opportunity to show your deep understanding of the question, even if it is a simple one.
1.Don't come to over confident state,
2.Stay calm,
3.Stay polite,
4.Listen carefully,
5.And explain answer in detail.
6.Don't feel that interviewee is at lower level than you [anyhow :) ]
To add to OLJ's answer- take the opportunity to discuss some of the why's of the question itself. Some questions are just for show (how would your reverse an array, write fizz-buzz, etc), but on any that are actual business cases, take the opportunity to show that you've actually done that before and you're aware of the potential pit-falls and failures that come inherant in the scenario itself.
"That's an interesting problem! So your applications spend a lot of their time reversing linked lists do they? Can I ask why that is?"
Don't talk down to the interviewer, but there's nothing that says simple questions deserve simple answers. I say go as deep as you'd like with your answer as long as you aren't putting the interviewer(s) off by perceived cockiness. I believe a good interviewer will cater an interview to the interviewee's responses. If you are willing to demonstrate your smarts, I'm sure the questions will become more challenging as the interview moves forward.
This said, there is a bit of a red flag here. Not being challenged in the interview may translate to not being challenged on the job. An interview goes both ways -- the potential employer is certainly sizing you up and you should be doing the same of them. Make sure the position will be a good fit for both of you and see if you can't get some insight into the type of project work (challenging or not) to which you may be assigned.
Best of luck.