SOLUTION: Catching up. A sailboat leaves port and travels due south at an average speed of 9mph. Four hours later a motorboat leaves the same port and travels due south at an average speed o

Question 159989: Catching up. A sailboat leaves port and travels due south at an average speed of 9mph. Four hours later a motorboat leaves the same port and travels due south at an average speed of 21 mph. How long will it take the motorboat to catch the sailboat?
Answer by KnightOwlTutor(293) (Show Source): You can put this solution on YOUR website!
X=time it takes for the motorboat to catch up
X+4=time that it takes the sailboat to cover the same distance
(X+4)9=21X
Use the distributive property
9X+36=21X
Subtract 9X from both sides
36=12X
Divide both sides by 12
X=3
It takes the motorboat 3 hours to catch up with the sailboat
To double check that it is the right answer plug in 3 for the x variable. Both sides of the equation must be equal.
(X+4)9=21X
7*9=21*3
63=63

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