Question : The ratio of the outer and the inner circumferences of a circular path is 11 : 7. If the path is 20 metres wide, then what is the radius of the inner circle?
Option 1: 20 metres
Option 2: 55 metres
Option 3: 65 metres
Option 4: 35 metres
Correct Answer: 35 metres
Solution :
The circumference of a circle is given by the formula
Given that the ratio of the outer and the inner circumferences of the circular path is 11 : 7.
Given that the width of the path (which is the difference between the outer and inner radii) is 20 metres.
Substituting the first equation into this gives:
Hence, the correct answer is 35 metres.