## stupidinmath Group Title --- 7 months ago 7 months ago

1. Starr_DynastyT Group Title

@shamil98

2. stupidinmath Group Title

A= big semicircle.. what's next?

3. MayankD Group Title

50pi

4. MayankD Group Title

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

5. oldrin.bataku Group Title

this is SAT yes? I remember this one

6. Haleo Group Title

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

7. Haleo Group Title

Isn't it right?

8. oldrin.bataku Group Title

|dw:1389510061781:dw|

9. oldrin.bataku Group Title

|dw:1389510085539:dw|

10. oldrin.bataku Group Title

|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. oldrin.bataku Group Title

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

12. oldrin.bataku Group Title

|dw:1389510292746:dw|

13. liliegirl Group Title

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. oldrin.bataku Group Title

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. liliegirl Group Title

|dw:1389510798177:dw|

16. stupidinmath Group Title

so.. also find that part and add it?

17. liliegirl Group Title

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

18. oldrin.bataku Group Title

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

19. stupidinmath Group Title

oh. right

20. stupidinmath Group Title

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

21. liliegirl Group Title

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

22. oldrin.bataku Group Title

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

23. stupidinmath Group Title

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