Question

The radius of the inner circle is 9yd.
The difference between the outer diameter and the inner diameter is 2 yd.


What is the radius of the outer circle?

• A. 9 yd
• B. 11 yd
• C. 10 yd
• D. 8 yd

Answer 1

The correct option is C 10 yd

Radius OR of the inner circle = 9 yd

We have to calculate the radius of the outer circle.

As we know,
Diameter = 2 × Radius
Diameter of the inner circle = 2 × 9 yd
= 18 yd

Difference between the diameter of the outer circle and the inner circle = 2 yd

Which means, diameter of the outer circle $-$ diameter of the inner circle $=$ 2 yd

Diameter of the outer circle - 18 yd = 2 yd
Diameter of the outer circle = 2 yd + 18 yd
= 20 yd

Radius = Diameter ÷ 2
$\therefore$ Radius OT of the outer circle = 20 yd ÷ 2
= 10 yd