The area enclosed by the circumference of two concentric circles is 364.5 cm². If the circumference of the inner circle is 88cm, calculate the radius of the outer circle.

The correct answer is: 17.66 cm

It is given that Circumference of inner circle = 88 cm
2  r =  88
2 ×  ×  r  =  8
r  =  14 cm
Let radius of outer circle = r₁
Area enclosed by the circumference of two concentric circles = 364.5 cm²
i.e. Area of outer circle – Area of inner circle = 364.5 cm²
 (r₁)²  -  r²     = 364.5
 × (r₁)²  -  × (14)²  = 364.5
((r₁)² – 14²) = 364.5
((r₁)² – 14²   = 
(r₁)² = 311.977
r₁  = 17.66 cm