Question

What is the circumference of a circle with a radius of $ 30 $ inches?

Answer 1

Hint: As we know that the circumference of a circle is the length of the boundary of the circle. And the distance between the center and any point on the circumference is known as the radius of the circle. In this question we have the radius $ = 30inches $ and we have to find the circumference. We know the formula of circle of circle is $ 2\pi r $ .

Complete step by step solution:
Let us first draw the image of the circle with radius.

In the above we have denoted the circumference of the circle and OA is the radius, $ OA = 30 $ inches.
Now we know the formula of circumference $ 2\pi r $ , where $ r $ is the radius of the circle.
Putting the value back in the formula we have $ C = 2 \times \pi \times 30 $ , it gives us the value $ 60\pi $ .
Hence the required circumference of the circle is $ 60\pi $ .
So, the correct answer is “ $ 60\pi $ inches”.

Note: We can also put the value of $ \pi $ in the formula and then get the value in numbers. The value of $ \pi $ is $ 3.1416(approx) $ . So the required circumference will be $ 2 \times 3.1416 \times 30 = 188.496 $ or by rounding off the value is $ 188.5 $ inches. We should note that $ \pi $ is a constant and in calculation we generally use its approximate value as $ 3.1416 $ or $ \dfrac{{22}}{7} $ .