An ASTM grain size determination is being made from a photomicrograph of a metal at a magnification of 1X. What is the ASTM grain size number of the metal if there are 992 grains per square mm?

An ASTM grain size determination is being made from a photomicrograph

1.	An ASTM grain size determination is being made from a photomicrograph of a metal at a magnification of 1X. What is the ASTM grain size number of the metal if there are 992 grains per square mm?
A.	6
B.	7
C.	7.92
D.	8.91
Answer» C. 7.92