# ML Aggarwal Solutions Class 9 Mathematics Solutions for Mensuration Exercise 16.3 in Chapter 16 - Mensuration

Question 2 Mensuration Exercise 16.3

Find the radius and area of a circle if its circumference is 18π cm.

Consider the radius of the circle = r

Circumference = 2 πr

We know that

2 πr = 18π

So we get

2r = 18

r = 18/2 = 9 cm

Here

\begin{aligned} &\text { Area }=\pi \mathrm{r}^{2}\\ &\text { Substituting the value of } r\\ &=\pi \times 9 \times 9\\ &=81 \pi \mathrm{cm}^{2} \end{aligned}

Video transcript
"hello and welcome my dear students i am rishabh the math pseudonym leader and i'm here a new question it is find the radius and the area of circle if its circumference is 18 pi centimeters so without wasting much time let's have a look at the solution so let's radius of circle vr and we know that circumference is 2 pi r we know that we have been given circumference as 18 pi centimeters so 2 by r is equals to 18 pi which means solving it further we get r as 18 by 2 which is nothing but 9 centimeter so we have found out the radius and we are left with area so area of circle is nothing but pi r square which is nothing but pi into 9 into 9 which is nothing but equals to 81 pi centimeter square so i hope my students got this question well do subscribe our channel for the regular updates see you next time bye"
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