Question

If the difference between the circumference and diameter of a circle is $30cm$ then what is the radius of the circle?

• A. $7cm$
• B. $15cm$
• C. $22cm$
• D. $2cm$

Answer 1

The correct option is A $7cm$

Let r be the radius of the circle
Then $2\pi r-2r=30\Rightarrow 2r(\pi -1)=30$
$\Rightarrow r(\frac{22}{7}-1)=15\Rightarrow r\times \frac{15}{7}=15\Rightarrow r=\frac{15\times 7}{15}=7cm$