The cunninghams are moving across the country. mr. cunningham leaves 3 hours before mrs. cunningham. if he averages 55mph and she averages 75mph, how long will it take mrs. cunningham to overtake mr. cunningham?
His 3-hour head start puts Mr. Cunningham 165 miles ahead of her. She makes that up at the rate of (75 -55) = 20 mph, so will overtake Mr. Cunningham after (165 mi)/(20 mi/h) = 8.25 hours.
