1. The problem statement, all variables and given/known data Given that there are 10-2 Ellipticals per Mpc3 and my garden telescope can reach to 14 mag. How large an area of sky would I need to survey to find 100 Elliptical galaxies ? (assume the typical absolute magnitude for an Elliptical galaxy is -21 mag). 2. Relevant equations d=100.2(m-M-25) n=N/V 3. The attempt at a solution by substituting m=14 and M=-21 into the first equation I found d=100Mpc, which indicates the volume of sky I could possibly observed is 4/3⋅π⋅d3 = 4188790 Mpc3, using the second equation n=N/V , where n=number density, I have 10-2 = 100/V, thus V=10000Mpc3, which is the volume I need to observed to find 100 galaxies. with these values, how can I find how large the area of sky I need to survey?