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Answer 12:

It is given that, and

We know that the circumference C of semicircle of radius be r is


The inside perimeter of running track is the sum of twice the length of straight portion and circumferences of semicircles. So,
inside perimeter of running track = 400 m
2l+2πr=400 m
2×90+2×227×r=400 m
r=220×72×22=35 m
Thus, radius of inner semicircle is 35 m.

radius of outer semi circle r' = 35 +...


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