## anonymous 2 years ago ---

1. anonymous

@shamil98

2. anonymous

A= big semicircle.. what's next?

3. anonymous

50pi

4. anonymous

Just remove the semicircle on the left and place it in the gap on the right

5. anonymous

this is SAT yes? I remember this one

6. anonymous

$a= \pi*r ^{2}$ $a= ( \pi * 10^{2} ) /2 = 157.079$

7. anonymous

Isn't it right?

8. anonymous

|dw:1389510061781:dw|

9. anonymous

|dw:1389510085539:dw|

10. anonymous

|dw:1389510103621:dw| so the area is equivalent to just the top semicircle... we merely moved the piece under the line to fill the hole to the right

11. anonymous

the radius is very clearly $$r=10$$ ergo the area is $$A=\pi r^2=\pi(10)^2=100\pi$$

12. anonymous

|dw:1389510292746:dw|

13. anonymous

It is a semicircle so you need to divide by 2. The answer is 50pi + 25pi over 2. $\frac{ 75\pi }{ 2 }$ is the answer.

14. anonymous

oops -- good catch. you do need to multiply by $$1/2$$ to get just the top:$$\frac12\cdot100\pi=50\pi$$that being said, it is NOT $$\frac12(50\pi+25\pi)$$

15. anonymous

|dw:1389510798177:dw|

16. anonymous

so.. also find that part and add it?

17. anonymous

You need to add that because it is also shaded. The area of that part is 25pi over two.

18. anonymous

@liliegirl that part is precisely the part we moved to fill in the top semicircle. it is now accounted for...

19. anonymous

oh. right

20. anonymous

so.. the answer is.. 314.16 right? thanks guys

21. anonymous

@oldrin.bataku Ahhh, Sorry, I didn't notice.... :)))

22. anonymous

@stupidinmath no it's half of that, i.e. $$50\pi$$

23. anonymous

oh.. since its a semi circle.. k thanks :)