A composite rod made of three rods of equal length and cross-section as shown in the fig. The thermal conductivities of the materials of the rods are K/2, 5K and K respectively. The end A and end B are at constant temperatures. All heat entering the face, A goes out of the end B and there being no loss of heat from the sides of the bar. The effective thermal conductivity of the bar is

The figure shows the face and interface temperature of a composite slab containing of four layers of two materials having identical thickness. Under steady State condition, find the value of temperature $\theta$.

Three rods made of the same material and having the same cross-section have been joined as shown in the figure. Each rod is of the same length. The left and right ends are kept at 0°C and 90°C respectively. The temperature of the junction of the three rods will be: