A composite bar of two sections of each of length 100mm, 150mm. When force is applied, all the sections causes an elongation of 0.1mm. What will the resultant strain on the bar be?

In a bar of different sections, the resultant strain is the algebraic sum of the individual stresses.

Strain= Elongation/Length

Strain in section 1 = 0.1/100
Strain in section 2= 0.1/150
Resultant strain = 0.001+0.0006 = 0.0016