Question

The circumference of two concentric circles are 121 cm and 154 cm. Calculate the difference between their radii ​

Answer 1

Answer:

circumference of bigger circle= 2πr1

154=2πr

154/2π =r1

circum. of smaller circle= 2πr2

121 =2πr2

121/2π=R2

difference r1-r2=154/2π- 121/2π

=33/2π

Answer 2

Answer:

hence answer is 10.25 cm

Step-by-step explanation:

let r be the radius of small cocentric circle and r' be the radius of large cocentric circle .

now

circumference of smaller circle=2×22÷7×r

121= 2×22÷7×r

121×7÷2×22= r

or r = 121×7÷2×22

r = 11×7÷2×2

r = 77÷4

r = 14.25cm

now circumference of bigger circle = 2×22÷7×r

154 = 2× 22÷7×r

154×7÷2×22= r

or r = 154×7÷2×22

. r = 7×7÷2

r = 49÷2

r = 24.5 cm

now according to question ..

difference between the radii of the two circles = 24.5-14.25

= 10.25cm