One of the most efficient engines ever developed operates between 2100 K and 700 K. It’s actual efficiency is 40%, what percentage of it’s maximum possible efficiency is?

percentage efficiency of heat engine is η=Thot-TcoldThotx100---(1)given Thot=2100K, Tcold=700K  substitute given values in above equation(1)η=2100−7002100×100η=14002100×100η=2003%, this is maximum possible efficiency of the engine  given actual efficiency is 40%     percentage of actual efficiency   with respect to maximum possible efficiency is=actual efficiencymaximum efficiencyx100 =402003x100  percentage of actual efficiency   with respect to maximum possible efficiency=60%