Problem: if the length of an edge of cube p is thrice the length of an edge of cube q , what is the ratio of the volume of cube q to the volume of cube p ? 
Options: ['a ) 1 / 4', 'b ) 1 / 5', 'c ) 1 / 6', 'd ) 1 / 27', 'e ) 1 / 9']
d