Two conductors having thicknesses d1 and d2 , thermal conductivities K1 and K2 are placed one above the other. The equivalent thermal conductance is:
d1+d2K2d2+K2d12K1+K2
(d1-d2)(K1d2+K2d1)1(K1+K2)
K1K2(d1+d2)d1K2+d2K1
none of the above
Here, d1+d2kA=d1K1A+d2K2A So, K=K1K2(d1+d2)d1K2+d2K1