find the radius of the sphere.

The radius of two parallel sections on the same sphere are 9 and 12 cm, and the distance between them is 21 cm. Find the radius of the sphere.
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1 Answer

r       is radius of the sphere

x      is distance from center to the second parallel section

21-x     is distance from center to the first parallel section

 

r^2=122+(21-x)^2

r^2=92+x2

 

122+(21-x)^2=92+x^2

144+441-42x+x^2=81+x^2

585-81=42x

504=42x

x=12
by Level 1 User (160 points)

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