1. Estimate the number of dentists (a) in San Francisco and (b) in your town or city. 2. You are in.

1. Estimate the number of dentists (a) in
San Francisco and (b) in your town or city.

2. You are in a hot air balloon, 200 m
above the flat Texas plains. You look out toward the horizon. How far out can
you see that is, how far is your horizon? The Earth’s radius is about 6400 km.