O is the common centre of two concentric circles and radius of the bigger circle is 14 cm. Area of the smaller circle is half of the bigger circle. What is the radius of the smaller circle?

**(A)** 7 cm

**(B) ** cm

**(C)** cm

**(D)** 10 cm

**(E)** cm

It is given that radius of the bigger circle cm

Area of the bigger circle

It is also given that area of the smaller circle is half the area of bigger circle.

Therefore, Area of the smaller circle

Let radius of the smaller circle

We have area of the smaller circle

**cm**

Hence, the answer is **(B)**.

We can directly find the radius of the smaller circle given that area of the smaller circle is half of the bigger circle.

where is the radius of the smaller circle and is the radius of the bigger circle.