A red car and a blue car are traveling at the same speed. The red car drives 4 hours. The blue car drives an additional 45 minutes and goes 21 more miles than the red car. How fast are the cars going?
+130071 Let the speed of the two cars be S (mph)
So......the distance the red car goes in 4 hours + 21 miles = the distance the blue car goes in 4 + 3/4 hours = 4.75 hours
So
4S + 21 = 4.75 S subtract 4S from each side
21 = .75S divide both sides by .75
S = 28 (mph)
Another way to see this is that the blue car covers 21 miles in 3/4 hr
So 21/ (3/4) = 84 / 3 = 28 mph
