Final answer:
The number of potentially habitable Earth-like planets in the Milky Way is estimated to be around 10 billion, based on the probability of having rocky planets in habitable zones around a portion of the galaxy's 100 billion stars and data from the Kepler mission.
Step-by-step explanation:
Based on discoveries to date, and considering the approximations provided by astronomers and the results from missions like Kepler, the number of potentially habitable Earth-like planets in our Milky Way galaxy is around 10 billion. The Milky Way is estimated to have about 100 billion stars, and with the assumption that 50% of these stars have planetary systems, 10% have a rocky planet in the habitable zone, and other sequential probability reductions for benign environments, potential for life, and chances of intelligent life, it leads to the possibility of several instances of intelligent life. Additionally, Kepler data and analyses suggest that small planets and 'super Earths' are common, with approximately one quarter of stars having exoplanet systems, making the existence of at least 50 billion planets likely in our galaxy.