Question

The circumference of two concentric circles are 121cm and 154cm.calculate the difference between their raddii

Answer 1

Let the radius of the smaller circle be r1 and that of the larger circle be r2
Circumference of smaller circle, c1 = 121 cm
Therefore,
2[tex] \pi [/tex]r1 = 121                                          ......(1)
Circumference of larger circle, c2 = 154 cm
2$\pi$r2 = 154                                          ......(2)
Subtracting (1) from (2) , we get:
2 x 22/7(r2 - r1) = 154 - 121
∴(r2 - r1) = $\frac{33 X 7}{2 X 22}$
∴(r2 - r1) = $\frac{3 X 7}{2 X 2}$
∴ r2 - r1 = $\frac{21}{4}$