Question

If 30 per cent of all stars are of suitable type for life to develop, 90 per cent of all stars have planets, and 70 per cent of planetary systems have one planet or moon at a suitable distance from the star, what fraction of stars have a planet suitable for life? Roughly how many such stars would there be in our Milky Way Galaxy?

Pasachoff, Jay M.,Filippenko, Alex. The Cosmos (p. 641). Cambridge University Press. Kindle Edition.

Answer 1