Question

Two concentric circles have radius in the ratio 10:6 forms a ring. The area of the ring is 4096 cm2 . Find the measurement of the radii.​

Answer 1

Answer:

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Step-by-step

The areas of two concentric circles forming a ring are 154 sq. cm and 616 sq. cm. The breadth of the ring is

A

21 cm

B

56 cm

C

14 cm

D

7 cm

Medium

Answer

Correct option is

D

7 cm

Breadth of the ring is equal to the difference between the radius of the outer circle and the radius of the inner circle

Let the radius of the outer circle be r2 and that of the inner circle be r1

Given that the area of outer circle is 616 cm2

∴ πr22=616 cm2

⇒r22=22616×7=196 cm2

∴r2=14 cm

Also, the area of the inner circle is 154 cm2

∴ πr12=154 cm2

⇒r12=22154×7=49 cm2

∴r1=