SOLUTION: car A and car B enter an expressway at the same time and same place and head the same direction. car A travels at 70 miles per hour. If after 2.5 hours car B is 50 miles behind car

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Question 654156: car A and car B enter an expressway at the same time and same place and head the same direction. car A travels at 70 miles per hour. If after 2.5 hours car B is 50 miles behind car A what is the speed of car B
Answer by Edwin McCravy(20060) About Me  (Show Source):
You can put this solution on YOUR website!
car A and car B enter an expressway at the same time and same place and head the same direction. car A travels at 70 miles per hour. If after 2.5 hours car B is 50 miles behind car A what is the speed of car B.
How to do it in your head:

They've separated 50 miles in 2.5 hours so they would separate
100 miles in 5 hours or 20 miles in 1 hour. So car B was going 
20 mph slower or 50 mph.

How to do it by algebra:

         rate  ×  time  =  distance    
car A     70       2.5       175 
car B      x       2.5       2.5x

             The equation comes from:

                            %28matrix%283%2C1%2Ccar%2C%22B%27s%22%2Cdistance%29%29 = %28matrix%283%2C1%2Ccar%2C%22A%27s%22%2Cdistance%29%29 - 50

                                2.5x = 175 - 50
                                2.5x = 125
                                   x = 50 mph     

Edwin