<PRE><B>Question 951049</B>
A hollow metal sphere has an internal radius of 20cm and an external radius of 30cm.
 Given that the density of the metal is 7.8g/cm^3, find the mass of the sphere, expressing ur answer in kg.
:
Find the vol of the outer and inner spheres {{{V = 4/3}}}{{{pi*r^3}}}
{{{4/3}}}{{{pi*30^3}}} = 113097.3355
{{{4/3}}}{{{pi*20^3}}} =  33510.3216
--------------------------------------Subtraction gives vol of metal
differ:  79587.014 cu/cm
Find the weight in grams
7.8 * 79587.014 = 620778.71 grams
find the weight in kg
{{{620778.71/1000}}} = 620.78 kg


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