Re: A brown bear's back paw prints measure 8' x 11'. How big would the bear be?

You really need to be a local tracker to answer this question, as there are 
so many 'ifs' and 'buts'.  

The first question is - what is the size range of the bears in your area ? 
There are probably different races in different parts of Alaska.  Males, 
females and young probably all have different sized feet in proportion to 
their weight, and each individual's weight is going to vary with its 
condition.  If you knew the range of sizes of the local bears, their likely 
condition at the appropriate time of year and the range of sizes of 
footprints, you might be able to attempt an answer.  The Inuit have this  
skill, and can estimate a polar bear's condition from the shape of the 
individual pads of the foot.

Footprints are fascinating pieces of evidence for the presence and 
behaviour of wild animals, but they rarely give accurate information of the 
kind you require.  There are so many variables.  Was the animal walking on 
a slope ?  Which gait was it using, and at what speed ?  How firm was the 
substrate in which the prints were found ?  How long was it since the 
tracks were made - they may change size as the mud dries out or the snow 
melts.

Also - what did you measure ?  Was it the bottom of the imprint, where the 
animal's foot was actually resting, or the squeezed out mud on the sides ? 
Did you include the claws in your measurement ?  I expect that if you had 
measured several prints from the track, you would have found them to be 
different sizes, as the bear moved from firm to soft substrate, turned and 
paused.

Sorry to be so unhelpful, there are a lot of interesting questions to asked 
about footprints, but the one you chose to ask is a difficult one to answer 
from a distance.  Why not start collecting casts and photos of footprints 
of your local wildlife, and find out some of the answers for yourselves ?  
As for your bear prints, I would ask a local hunter to come in and look at 
them - or even better, two or three hunters, and listen to them argue !

I wish I had bears around my school !