## anonymous one year ago HELP WILL MEDAL AND FAN! Find the area of the circle: Inner radius is 4cm, Outer radius is 9cm.

1. anonymous

Here are the options. A) 78.5cm^2 B) 31.4cm^2 C) 157cm^2 D) 204.1cm^2

2. ganeshie8

are you trying to find the area of region between below two circles ? |dw:1440600185673:dw|

3. Astrophysics

Note the area for a circle is $A_{circle} = \pi r^2$

4. anonymous

The diagram I was given asked me to figure out the area of the shaded region of the circle it showed me. The entire ring of the circle was faded in, but the middle part with the hole was not. To answer your queston yes I think.

5. Astrophysics

|dw:1440600531344:dw| so like this

6. anonymous

Yes except colored all the way in the ring part.

7. ganeshie8

|dw:1440600652512:dw|

8. Astrophysics

Show off!

9. ganeshie8

definitely! ;)

10. anonymous

Yes the bottom one looks like it.

11. ganeshie8

there is a little trick to get that black area

12. ganeshie8

do u remember how to find area of full circle ?

13. anonymous

Nope.

14. ganeshie8

you will need to know that before attempting this problem

15. ganeshie8

lets do a quick problem maybe

16. anonymous

K

17. ganeshie8

Find area of region interior to below circle of radius 3 units : |dw:1440600874779:dw|