U.S. home price gains slowed for the fifth straight month in August as higher mortgage rates lowered home sales. The S&P CoreLogic Case-Shiller 20-city home price index, released Tuesday, increased 5.5 percent in August compared with a year earlier. Sales of existing homes have dropped for six straight months, and sales of new homes have fallen for the past four. Prices rose the most in Las Vegas, San Francisco and Seattle. But price gains have slowed compared with a year earlier in 14 of the 20 cities tracked.