Why two layers of cloth of equal thickness provide warmer covering than a single layer of cloth of double the thickness?

The thickness of thin layer adsorbent in TLC is about

A spherical iron ball 10 cm in radius is coated with a layer of ice of uniform thickness that melts at a rate of 50 cm^(3)//min . When the thickness of ice is 5 cm, then find the rate at which the thickness of ice decreases.

A spherical iron ball of radius 10 cm , coated with a layer of ice of uniform thickness , melts at a rate of 100picm^(3)//min . The rate at which the thickness decreases when the thickness of ice is 5 cm , is a)1 cm/min b)2 cm/min c) (1)/(376) cm/min d)5 cm/min