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A running track is the ring formed by two concentric circles. If the circumferences of the two circles differ by 20 pi feet, how wide is the track in feet?

 Nov 15, 2020
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The circumference of the  inside circle can  be expressed as 2pi R1

The circumfernce of the outside circle can be expressed as  2piR2

 

So

20pi  = 2pi R2 - 2pi R1

20pi  =  2pi  (R2 - R1)     divide both sides by 2 pi

 

10  = R2 - R1    [ the track is 10 ft wide  ]

 

cool cool cool

 Nov 15, 2020

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