## anonymous one year ago http://media.education2020.com/evresources/2072227_circle_in_circle.png Find the circumference of the larger circle if the area of one of the smaller circles is 48 pi in2. Will give medal and fan and testimony

1. jim_thompson5910

" the area of one of the smaller circles is 48 pi in2" use this info to find the radius of the smaller circle

2. jim_thompson5910

Area of a circle $\Large A = \pi*r^2$

3. anonymous

Would 48 be the diameter?

4. jim_thompson5910

no, 48pi is the area

5. jim_thompson5910

A = 48pi

6. wolf1728

48 = PI * r^2 r^2 = 48 / PI

7. anonymous

So would i do 48*pi? Im so confused on this :(

8. jim_thompson5910

$\Large A = \pi*r^2$ $\Large 48\pi = \pi*r^2$ $\Large 48 = r^2$ the pi's cancel. Solve for r

9. anonymous

So this$\sqrt{48}=r ^{2}$

10. jim_thompson5910

more like $\Large r = \sqrt{48}$

11. jim_thompson5910

12. anonymous

I got 6.92 for the answer

13. wolf1728

Here's a quick answer: It appears that the smaller circle has a radius that is .5 the radius of the larger circle. When calculating area, when you double the size the area increases FOUR times. SO, area of larger circle = 4 * 48 = 192

14. jim_thompson5910

it wants the circumference of the larger circle

15. anonymous

Im really sorry that confused me even more :( like all my answer choices are in radical form

16. wolf1728

17. jim_thompson5910

|dw:1436235139053:dw|

18. jim_thompson5910

|dw:1436235225907:dw|

19. anonymous
20. jim_thompson5910

|dw:1436235275013:dw|

21. jim_thompson5910

Now use the circumference of a circle formula $\Large C = 2*\pi*r$ You'll plug in r = 2*sqrt(48)

22. anonymous

Ugh...this is not helping me not be confused. Really sorry for taking up so much tome

23. anonymous

*time

24. anonymous

25. jim_thompson5910

@ANA789 do you see how I got the values in my drawing?

26. anonymous

@jim_thompson5910 Yeah I got that but the answer i got was the same and it was wrong

27. jim_thompson5910

when you plug r = 2*sqrt(48) into that circumference formula, what do you get?

28. anonymous

13.85

29. jim_thompson5910

leave it in radical form though

30. anonymous

I dont know how to put that in radical form

31. jim_thompson5910

|dw:1436235731159:dw|

32. jim_thompson5910

|dw:1436235759458:dw|

33. jim_thompson5910

|dw:1436235791532:dw|

34. jim_thompson5910

|dw:1436235814441:dw|

35. jim_thompson5910

the only thing left to do here is to simplify the root

36. anonymous

Yeah I got 87.06 for that

37. jim_thompson5910

simplify $$\Large \sqrt{48}$$ to get ??

38. jim_thompson5910

hint: 48 = 16*3

39. anonymous

OH!! I SEE NOW!! OKay then thank you :) I know the answer now haha i feel dumb!

40. jim_thompson5910

its ok, your answer would work if they wanted the approximate result