Question

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


What is the radius of the outer circle?

• A. 11 m
• B. 9 m
• C. 10 m
• D. 8 m

Answer 1

The correct option is C 10 m

Radius OR of the inner circle = 9 m

We have to calculate the radius of the outer circle.

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

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

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

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

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