## hba 2 years ago If the radius of a circle is increased by 10 % then the area is increased by,

1. tkhunny

$$\pi r^2$$ $$\pi (r*1.1)^{2} = 1.21\cdot\pi r^{2}$$ What do you think?

2. hba

@hartnn Yeah lol ? It is a circle but it is a very diff ques..

3. hba

@tkhunny You are welcome to provide hints and explain

4. tkhunny

Already did. Radius increased by 10% -- r*1.1 Area is increased by ???

5. hba

Please explain how did you do the first step

6. tkhunny

Area of a Circle = $$\pi r^{2}$$, given the radius. That's the first step.

7. hba

I know that the Area of a circle = pi r^2

8. tkhunny

New Radius is 10% greater than old radius. R = r*1.1 Area of new circle: $$\pi R^{2}$$.

9. hba

Got it what next ?

10. tkhunny

Raio of New Area to Old Area $$\dfrac{\pi R^{2}}{\pi r^{2}}$$.

11. hba

Ratio*

12. tkhunny

*Ratio - right A little algebra $$\dfrac{\pi R^{2}}{\pi r^{2}} = \dfrac{R^{2}}{r^{2}} = \dfrac{(1.1\cdot r)^{2}}{r^{2}} = \dfrac{1.1^{2}r^{2}}{r^{2}} = 1.1^{2} = 1.21$$ And we see a 21% increase!

13. hba

Thank you.