What is the fraction representing the metal used in the shell of a 20 gauge steel casket?

In the context of the thickness of steel used in caskets, the gauge number is inversely related to the thickness of the metal. A lower gauge number signifies a thicker metal. For 20 gauge steel, the appropriate thickness is approximately 0.036 inches.

When considering the metal used relative to a standard measurement, the fraction that represents the metal in the shell of a 20 gauge steel casket is 1/20, since the gauge indicates that there are 20 units of thickness when measuring it in terms of a standard inch.

This understanding of gauge and its relationship to thickness makes it clear why 1/20 is the correct representation of the metal used in the shell of a 20 gauge steel casket. The other choices reflect different gauges or thicknesses that do not accurately portray the specifications associated with 20 gauge steel.