The weekly average rate borrowers were quoted on Zillow Mortgage Marketplace for thirty-year mortgages remained relatively flat during the past week. Last week's rate was 5.10 percent, up slightly from 5.08 percent the week prior, according to the Zillow Mortgage Rate Monitor, compiled by leading real estate Web site Zillow.com®. Meanwhile, rates for 15-year fixed mortgages decreased to 4.73 percent, down from 4.77 percent and 5-1 adjustable rate mortgages also decreased, down to 4.65 percent from 4.71 percent the week prior.