How many stars are there?

In my student days in high school, we were taught that a hundred billion stars in our galaxy existed (Milky Way).

Then they talked about two hundred billion stars, and currently says between one billion and four hundred billion stars in our galaxy. 

Same with galaxies today and based on extrapolation based on observable in certain areas of space , you will reach the number of two hundred billion galaxies.
          But telescopes continue to improve and increasingly showing galaxies and therefore more stars, which incidentally, also increases the number of planets and in turn greatly increases the prospect of extraterrestrial life.