SOLUTION TO EXERCISE 1

One degree is 60 arcminutes, so let's estimate that 
one square degree = 60 * 60 = 3600 square arcminutes.  
That means there are 3600 * 41,000, or about 
150,000,000 square arcminutes in the sky.  

I'd go cross-eyed counting all the blobs on the photograph, so I'll 
count the galaxies in one-quarter of the photo and multiply by four.  
I wind up with about 150 galaxies in that quarter; so the whole photo 
contains about 180 * 4 = 720 galaxies.

So if this patch of sky in the photo is typical of the sky as a whole, 
then there are about

  (720 galaxies per square arcminute) * (150 million square arcminutes)

 = 108,000 million, or 108 billion galaxies in the sky.  Since I've made
   several ballpark estimates, I'll pick the nearest round number and say
   that there are about 100 billion galaxies in the observable universe.