SOLUTION: A sphere circumscribes a cube of side 4cm. a) What is the radius of the sphere? b) Find the ratio of the volume of the sphere and cube

Algebra ->  Circles -> SOLUTION: A sphere circumscribes a cube of side 4cm. a) What is the radius of the sphere? b) Find the ratio of the volume of the sphere and cube      Log On


   



Question 1129803: A sphere circumscribes a cube of side 4cm.
a) What is the radius of the sphere?
b) Find the ratio of the volume of the sphere and cube

Answer by math_helper(2461) About Me  (Show Source):
You can put this solution on YOUR website!
If s is the length of the sides of the cube, then +r%5Bsphere%5D+=+s%2Asqrt%283%29%2F2+ <—<<< r is 1/2 the diagonal length of the cube, which is +sqrt%28s%5E2+%2B+s%5E2+%2B+s%5E2%29+
a) +r%5Bsphere%5D+=+2sqrt%283%29+cm or about 3.464cm

b) Because r can be expressed as a function of s, the ratios can be found in general (the s%5E3 will cancel), without the need for a specific radius:
+V%5Bcube%5D+=+s%5E3+


or about 2.7207.