The way you answer it depends on the client.
One good answer is that it depends on the job requirements.
For a stressful gig where you are the sole developer with huge responsibility and tight deadline, it would be worth more than, say, a more straightforward role where you are a cog in the machine.
Another approach is to them them you are flexible and would like to learn more about the position first. It's not wrong for both parties to know a ballpark to avoid wasting time so you could give a wide range of 25%, but it's nice to not say a number because you kind of want to avoid making yourself a number and would be better getting to know each other so they are more in the mindset of wanting you, which makes you worth more.
Since nooone else mentioned hard numbers, I will.
I would say an average range for a good-great consultant is 200-300/hr, but the term is rarely more than 3 months with a client, and sometimes as small as 1 month.
Positions through contracting companies where they have less responsibility, on-boarding is easier, and the term is closer to 6 mo - 1yr, the rate is more like 100-150, though.
