## gabbyalicorn one year ago What is the exact area of a circle whose diameter is 18 cm?

1. jim_thompson5910

formula A = pi*r^2 pi = 3.14 approximately r = radius = half of diameter

2. gabbyalicorn

|dw:1433387436296:dw|

3. jim_thompson5910

ok so each answer is in terms of pi, so ignore the pi's for now

4. gabbyalicorn

5. jabez177

18 divided by 2

6. jim_thompson5910

diameter = 18 radius = half of diameter

7. gabbyalicorn

so 9

8. jim_thompson5910

yep

9. jim_thompson5910

then you plug that into A = pi*r^2

10. gabbyalicorn

3.14 x 18

11. jabez177

$3.14 \times 8 \times 8$

12. gabbyalicorn

200.96

13. gabbyalicorn

divide it by 2?

14. jabez177

Wait... Let me try this again...

15. jim_thompson5910

again, ignore the pi's

16. jim_thompson5910

every answer choice has a pi in it

17. gabbyalicorn

8x8 = 64

18. jim_thompson5910

but you found the radius to be 9, not 8

19. gabbyalicorn

9 x 8 = 72

20. jim_thompson5910

r^2 means r times r

21. jim_thompson5910

r = 9

22. gabbyalicorn

9 x8 x8 ?

23. gabbyalicorn

576

24. jim_thompson5910

idk how you're getting 9 x 8

25. jim_thompson5910

r^2 = r x r = 9 x 9 = ?? I replaced the 'r's with 9 since the radius is 9

26. gabbyalicorn

81?

27. jim_thompson5910