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# A hollow crystal is made of glass that is 3 cm thick. The ball has a radius to the outside surface of 8 cm.

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A hollow crystal is made of glass that is 3 cm thick. The ball has a radius to the outside surface of 8 cm.

What is the approximate volume of glass used to make the ball?

Use 3.14 to approximate π

Mar 1, 2019

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Volume of the 8cm sphere - volume of 5 cm sphere = glass volume

volume of a sphere = 4/3 pi r^3     Get your calculations on !

= 4/3 pi (8^3 - 5^3)   = 516 pi = 1620.2 cm^3

Mar 1, 2019
edited by Guest  Mar 1, 2019
edited by Guest  Mar 1, 2019
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you need to account for both sides...

-DBZ

DivideByZero  Mar 1, 2019
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No you don't......you are dealing with radii     one radius is  8 the inner is 5

ElectricPavlov  Mar 1, 2019
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whoops!!! sorry! Guess i dont know what im talking about DivideByZero  Mar 1, 2019
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since it is hollow, you need to take the whole volume minus the air inside

heres a diagram ish

|       |                      |       |

|       |         inside         |       |<------- outside glass

|       |                      |       |

3cm     2cm            3cm

<<---------8cm-------------->>

so, thats the ball

now we find volume

v=4/3 pi r2

8cm= 2144.66 cm

2cm=33.51cm

2144.66-33.51= 2111.15cm^2

hope that helped

-DBZ Mar 1, 2019
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Ooops....dbz      volume  is 4/3 pi r^3

Mar 1, 2019
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i put it in the google calc so either way it would be the same, i just messed up the formula, sorry

DivideByZero  Mar 1, 2019