Market sizing question: # of vending machines in the US

Hi All,

Just encountered the market sizing question specified in the title. My partner and I came up with two different approaches:

1. First, divide by the total US population into (i) urban and (ii) rural areas. Next, almost entirely disregard the rural areas, and focus on urban areas, which we further broke down into cities of (a) low, (b) medium and (c) high population density areas. For each of these three, we assigned an average number of people per vending machine (e.g., if high, then 1 vending machine for every 25 people, etc). Needless to say, we assigned weights / percentages along the way.
2. Divide by places where vending machines are commonly found, such as, office buildings, residental buildings, service places (e.g., gyms, libraries) and most importantly, public places and streets. Next, we sought to go about calculating number of office buildings and other categories, etc. We felt that this approach was more accurate but more time consuming compared to the above approach.

So the question is, (i) what do you think of our two approaches and how would you improve them?, and (ii) what other approaches would you recommend?

Thank you in advance,

PrepLounger