1. The problem statement, all variables and given/known data A rod is made of two sections joined end to end. The sections are identical, except the one is steel and the other is brass. While one end is held fixed, the other is pulled to result in change in length of 1.20 mm. By how much does the length of each section increase? 2. Relevant equations Strain = stress / E Stress = F/A delta L = 1/E x L 3. The attempt at a solution I know that E(steel) = 200x10^9 and E(brass) = 100x10^9 I know that the total length is L= L1 +L2, where L1 is the length of the steel and L2 is the length of the brass I know that the force and cross-sectional area is the same, so those don't matter. I feel that the delta L = 1/(E(steel)+E(brass))xL would be right, but i dont know where to find the value of L. or is it that delta L = 1/E(steel)xL1, where delta L = 1.20mm? but i feel that this is wrong because it says in the question that the whole rod lengthens that much. any suggestions?