If the sun's mass is about average, how many stars are there in the milky way galaxy? the mass of the sun is of the order of 1030 kg and the mass of the milky way galaxy is of the order of 1042 kg.

Just assume that the sun has the average mass of all the stars

Then divide the mass of the galaxy by the mass of the sun.

10^30 has 30 zeroes after it. 10^42 has 42 zeroes.

The answer would have 12 zeroes which concludes a trillion stars.