alainabbyboo22
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



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alainabbyboo22
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can someone help me out here ? i keep trying to solve it but i'm doing something wrong here .
@nubeer

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

alainabbyboo22
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1/3 n r^2 h ?

nubeer
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dw:1352739974313:dw

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

alainabbyboo22
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this is what i got for my answer . 47123.8898038

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

alainabbyboo22
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yes but now i'm confused on what to do . can you type the equation for me and i will solve ?

nubeer
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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

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

alainabbyboo22
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i did :
1/3 * pi * 30^2 * 50

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

alainabbyboo22
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what would i put there then ?

nubeer
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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.

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

nubeer
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dw:1352740718104:dw

nubeer
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ok can you see the picture now i just posted?

alainabbyboo22
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okay i see it . but what am i supposed to do ?

alainabbyboo22
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30 * 50 ?

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

alainabbyboo22
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yes

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

alainabbyboo22
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so 50^2 + 30 ^2 = c^2 ?

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

nubeer
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dw:1352741077853:dw

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

alainabbyboo22
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1.6

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

alainabbyboo22
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1600^2

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

alainabbyboo22
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40

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

alainabbyboo22
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A is my answer !!

nubeer
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yes its A :)

alainabbyboo22
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woops just double checked that ! its D . my bad !

nubeer
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lol.. sorry my bad too.. :P

alainabbyboo22
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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 !

nubeer
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lol you are most welcome anytime :)