How many hours on an average do academics in business and technology spend consulting for businesses?
I would say the mean over all of academia is very low, almost zero. I would even go so far as to say that the median amount of time is zero. However, this includes all professors from all fields. It is not impossible for a Professor of German Romantic Poetry to find businesses that need their expertise but I would image them few and far between. 

There is also the issue of contractual obligations. My current professorial contract states that during the academic year I cannot work for another institution as more than a "part time job" but during the breaks I could work for someone else full time. While this does not give concrete limits it is presumed here to be about 10 hours per week as a general maximum.

More applied professors I have met were officially funded by outside corporations so their research counted double as both consulting work and as their normal work load. So for them even during the academic year it could be over 40 hours per week.

So what I mean to say is that to get a useful answer you should probably be more specific about which fields you are interested in.