# How long will it take to temperatures of two solids to become equal?

If I have two solids with commmon area where they are touching each other, is there any way for calculating the time it will take to them to become equal? For example, I have two blocks of different materials with different temperatures. They touch each other on one side. Can I calculate the time until their temperatures become equal?

$$\Delta Q=\frac{\lambda S(T_2-T_1)}{L}\,\Delta t$$ Can I calculate $\lambda$ for my example as proportion of weights? $$\lambda_{r} = {m_{1}\lambda_{1}\over m_{1} + m_{2}} + {m_{2}\lambda_{2}\over m_{1} + m_{2}}$$

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