A cylinder
A of a material of thermal conductivity
K1 is surrounded by a cylindrical shell of inner radius equal to the cylinder.
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The shell is made of a material of thermal conductivity
K2. The two ends of the combined system are maintained at two different temperatures. If the effective thermal conductivity of the system is
4K1+ 5K29, ratio of outer radius of the shell to the radius of the cylinder is
(Answer upto two digit after the decimal point)