donovan and michael are racing around a circular 400 - meter track . if donovan runs each lap in 48 seconds and michael runs each lap in 40 seconds , how many laps will michael have to complete in order to pass donovan , assuming they start at the same time ?
"one way of approaching this question is by relative speed method 1 . speed / rate of donovan = distance / time = > 400 / 48 = > 50 / 6 2 . speed / rate of michael = distance / time = > 400 / 40 = > 10 relative speed between them = 10 - 50 / 6 = > 10 / 6 ( we subtract the rates if moving in the same direction and add the rates if moving in the opposite direction ) in order to pass donovan - distance to be covered = 400 , relative rate = 10 / 6 total time taken by micheal to surpass donovan = distance / rate = > 400 * 6 / 10 = > 2400 / 10 = > 240 no . of laps taken by michael = total time / michael ' s rate = > 240 / 40 = > 6 hence correct answer is 6 laps . e"
divide(divide(400, subtract(divide(400, 40), divide(400, 48))), 40)