Posted by Math's Noob on .
A hollow spherical metal ball has internal radius 1cm. If the metal is 1/2 cm thick, find the volume of metal ( Take pi equals 22/7)

Maths 
Reiny,
outer radius = 1.5 cm
volume (if solid metal) = (4/3)π r^3
= (4/3) π (1.5)^3
= 4.5π
Hollow part = (4/3)π(1^3 = 4π/3
so volume of metal = (9/2)π  (4/3)π
= (19/6)π
or appr. 9.95 , (nobody uses 22/7 for π, we all have calculators)