Question

Area enclosed between two circumference of two concentric circles is346.5cm if circumference of inner circle is88cm radius of outer circle

Answer 1

Let,

       Radius of inner circle = r

       Radius of outer circle = R

Circumference of inner circle = 88cm

2πr = 88

πr = 44

r =44/π

Area enclosed between two circumferences = 346.5 cm²

π ( R² - r²) = 346.5

π [R² - (44/π)²] = 346.5

(R² - 44*44/π²) = 346.5/π

R² - 1936/π² = 346.5/ π

Finally after some steps,

R² = 3025/ π²

R² = (55/π)²

R = 55/π

R = 55* 7/22

R = 5*7/2

R = 17.5 cm

Answer 2

first you calculate radius of of inner circle and keep radius in form of ,πthen by using area enclosed between of two concentric circles and

$\pi( {r1}^{2} - {r2}^{2} )$

then by solving you will get r2 =18(approx)