## alainabbyboo22 3 years ago Find the volume of a cone with radius 30 in and slant height 50 in. A. 3769.91 in3 B. 3768 in3 C. 113040 in3 D. 37699.11 in3

1. alainabbyboo22

can someone help me out here ? i keep trying to solve it but i'm doing something wrong here . @nubeer

2. nubeer

hmm can you tell me the formula for vol of cone?

3. alainabbyboo22

1/3 n r^2 h ?

4. nubeer

|dw:1352739974313:dw|

5. nubeer

volume = 1/3* pi *r^2*h|dw:1352740094367:dw| can you find h?

6. alainabbyboo22

this is what i got for my answer . 47123.8898038

7. nubeer

nop you used 50 in calculations.. as its not the height in this case.. can u see the diagram i drew?

8. alainabbyboo22

yes but now i'm confused on what to do . can you type the equation for me and i will solve ?

9. nubeer

well u first have to find the h.. h is the perpendicular height and its not given.. formula for cone is this. volume = 1/3* pi *r^2*h

10. nubeer

maybe you can do your steps here so i can point your mistake.

11. alainabbyboo22

i did : 1/3 * pi * 30^2 * 50

12. nubeer

ok.. half is right .. the place where u had put 50 that is wrong. its not 50

13. alainabbyboo22

what would i put there then ?

14. nubeer

ok.. would you able to see the picture if i draw here for u? because i posted pictures above but no respone about that from you.

15. nubeer

so i am not sure if you are able to see pictures or something wrong.

16. nubeer

|dw:1352740718104:dw|

17. nubeer

ok can you see the picture now i just posted?

18. alainabbyboo22

okay i see it . but what am i supposed to do ?

19. alainabbyboo22

30 * 50 ?

20. nubeer

do u see the "h" with the dotted line?

21. alainabbyboo22

yes

22. nubeer

ok find the value of "h" by Pythagoras theorem.

23. alainabbyboo22

so 50^2 + 30 ^2 = c^2 ?

24. nubeer

not exactly.. the slanting height is "c" the base is "a" and height is "b"..

25. nubeer

|dw:1352741077853:dw|

26. nubeer

so c^2=a^2+b^2 c=50, a= 30 , b= h can you find h now?

27. alainabbyboo22

1.6

28. nubeer

nooo.. 50^2 - 30^2 = h^2

29. alainabbyboo22

1600^2

30. nubeer

yes h^2 = 1600.. now take square root to find h.

31. alainabbyboo22

40

32. nubeer

good.. this is your h now.. volume = 1/3* pi *r^2*h h=40, r =30 now plug it in formula.

33. alainabbyboo22

34. nubeer

yes its A :)

35. alainabbyboo22

woops just double checked that ! its D . my bad !

36. nubeer

lol.. sorry my bad too.. :P

37. alainabbyboo22

haha its all good ! it just made sense but then i looked at my answer again and i'm like wait a minute .. lol thank you for helping me !

38. nubeer

lol you are most welcome anytime :)