A rail way 50m long, with initial temperature of 20degree celsius subjected to a great heat. How much will it expand when its temperature is tripled?
I wonder what tripled means, 60C? Temperature is normally thought of in physics as average kinetic energy, and temperature is on an absolute scale.
20C=297+20=317K
Tripling that is 951K
My gut tells me that the author is trying to trick you, for some silly purpose.
deltalength=length*coeffthermal*(951-317)