It’s the end of the semester, and sisters Sarah and Chelsea are eager to head home for the summer. It’s a long drive, and Sarah’s old car can manage an average speed of only 55 miles per hour, so she leaves early in the morning. An hour later, Chelsea follows her at an average speed of 75 miles per hour. How many hours will it take Chelsea to catch up to Sarah?

Question

It’s the end of the semester, and sisters Sarah and Chelsea are eager to head home for the summer.  It’s a long drive, and Sarah’s old car can manage an average speed of only 55 miles per hour, so she leaves early in the morning.  An hour later, Chelsea follows her at an average speed of 75 miles per hour.  How many hours will it take Chelsea to catch up to Sarah?

Henry · Answer

d1 = Sarah's distance d2 = Chelsea's distance. d2 = d1 + 55 Vc*T = Vs*T + 55 75T = 55T + 55 20T = 55 T = 2.75 h. = 2h-45 Min.