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Probability

Question
CBSEENMA9003722

A spherical iron shell with 8 cm external diameter weighs 1860 4 over 7 straight g.
Find the sick ness of the shell if the density of metal is 12 g/cm3 .

Solution
Let the inner radius be x cm.
External radius = 8 over 2 space cm equals space 4 space cm
Volume of metal = 4 over 3 straight pi left parenthesis 4 cubed minus straight x cubed right parenthesis space cm cubed
therefore space space   Mass of metal = 4 over 3 straight pi left parenthesis 4 cubed minus straight x cubed right parenthesis space.12 straight g
According to the question,
space space space space space space space space space 4 over 3 straight pi left parenthesis 4 cubed minus straight x cubed right parenthesis space 12 space equals 13024 over 7
rightwards double arrow space space space space space space 4 over 3.22 over 7 left parenthesis 4 cubed minus straight x cubed right parenthesis 12 equals 13024 over 7
rightwards double arrow space space space space space space 4 cubed minus straight x cubed equals 37
rightwards double arrow space space space space space space straight x cubed equals 64 minus 37 equals 27 equals 3 cubed
rightwards double arrow space space space space space space space space space space straight x space equals space 3 space cm
therefore    Thickness of the shell = 4 cm - 3 cm= 1 cm