1. The problem statement, all variables and given/known data Two metre rulers made of metal of linear expansivity 25*10-6/degrees C are calibrated at 0 deg celsius. One end of each of the metre rulers is fixed to a vertical wall and held side by side horizontally. One of the meter rulers is maintained at 0 deg.C and the other at 100 deg C,which two scale markings coincide with each other ? (ans: 40 & 40.1cm) 2. Relevant equations l = l0 (1+ alpha*theta) 3. The attempt at a solution For the metre ruler kept at 100deg.C , l = l0 (1+ alpha*theta) l = 1 (1 + 25*10-6 *100) l = 1.0025 mm So when the meter ruler at 100 deg C reads 1mm,the actual reading is 1.0025mm. I'm not sure if what I've found is relevant to this question,even if it is I don't know how to proceed from here. Hope someone can help. Thanx.