Central park is a rectangle with an area of 840 acres. It is 1/2 a mile wide. One acre is 43,560 square feet. Two people start at the southwest corner at 1:30 pm and start walking round the park in opposite directions. One walks at 9 mph, the other walks at 2 mph. How long until they meet again? It may help to remember that a mile is 5280 feet.