i think it took me about 15 or 20 minutes to walk from flamingo to Aria. I walked North on the strip and took the walkway across Las Vegas Blvd. in front of Planet Hollywood.

I took the tram from Aria to Bellagio to get back. I think it took a shade less time but to be honest I wasn't paying attention. The tram stop for Bellagio is in the back so you do have to walk through a bunch of shops and the whole casino before you get to the front doors.

the tram runs from Bellagio to Aria to Monte Carlo and back.