How many hours a week do you normally work?
Basically, in asking this question, the interviewer wants to see why king of employee are you? Are you someone who puts in their 8 hours a day and leaves, or are you someone you is a workaholic who stays behind long after the cleaning staff has left.
If you the former, then it shows that you don’t care about the work and are more of less interested in just putting in your number of hours and leaving. This shows that you are not invested in the job or the company. However, if it is the latter, the interviewer may take it as a fact that you might have issue with deadline and that you can’t complete you work in the allotted time. Or is may also indicate that they might have to pay you a fortune in overtime.
While answering this question, keep in mind that every company and every job is different. Hence, the actual work hours may differ for each company or for the industry you want to work in. A 10-hour shift may be the norm, of perhaps a 4-hour shift. You have to be careful not to miss the mark here, so you should be aware what they actual expectations are.
The trick to this question is to not actually give a definite answer. You can give a range or state something along the lines of the fact that it may actually vary every week depending on the workload of the week. Hint: this is by far the best response to the question as it shows you are aware that nothing is constant and are willing to do what is necessary. After all the workload may actually change depending on the week, such as when there is a project due or something happens at work. This answer shows that you are aware of your responsibilities and are not afraid of stepping up and doing what is necessary for the job and for the company (which is what the interviewer and the company want to hear anyway).
A typical work week is 40 hours long; in my current job, I put in the require amount of hours. However, I know that there are times when we must stay back to finish up some work in order to meet a deadline, or due to some unforeseen circumstances, hence I have no qualms in staying back and working late in those times.