A 30.0 cm long metal rod expands by 0.0650 cm when its temperature is raised from 00C to 100°C. A second rod of different metal and of the same length expands by 0.0350 cm for the same rise in temperature. A third composite rod, also 30.0 cm long, is made-up of pieces of each of the above metals placed end to end and expands by 0.0580 cm when temperature is increased from O°C to 100°C. The length of the longer portion of the composite bar in cm at 0°C is