January 2008 SAT Hard Math Question HELP #18

muhammad9211
Sun, 28 Jul 2013 09:30:35 +0000

@xiggi, ur method is valid if distance travelled is the same? What if he travelled 15 miles at 20mph and 10 miles at 15mph. Would it work?
I only use that formula for rate of work. Good to know it works for these as well.