A student is tired of counting the individual rail sections around the bumper-car track. She starts to think of them as one long rail. She wraps a string around the outside. What does she do next?

Step-by-step explanation:

She should take the distance between two rails and divide the total length of the string with the distance between two rails.

No. of rails

Perimeter is defined as the boundary of a given area. When the student thinks all the rails of the car bumper track as one long rail she is cosidering the boundary. So the length of the string she wraps around is the perimeter.

Now let us consider she needed 400 m string to wrap around the area. And distance between two rail is 20cm.

Therefore the number of rails

                                                 = 2000 rails.