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5-31.

Mervin and Leela are in bumper cars. They are at opposite ends of a -meter track heading toward each other. If Mervin moves at a rate of  meters per second and Leela moves at a rate of meters per second, how long does it take for them to collide?  

A diagram of the problem.

Let and

Remember Mervin is starting at  because he is on the far left. His growth rate is m/s to the right.

So the equation for Mervin's position is , but the is not needed so is sufficient.

Do the same for Leela. Remember that her growth is negative and her starting position is different

Since Mervin and Leela will meet in the same position, set . This is like solving a system of equations using the equal values method.