Here in Singapore, "working" is the standard term used in schools to refer to the written steps in solving a maths problem (as ajb said). I guess this means it'

Here in Singapore, "working" is the standard term used in schools to refer to the written steps in solving a maths problem (as ajb said). I guess this means it's simply BrE (which Singapore English is a cousin of). I know Americans use "work" for the same purpose instead. > Using a gerund as a noun seems very unconventional and incorrect almost by definition. In English, gerunds are nouns (by definition). In "his singing was terrible", singing is a noun. Furthermore, gerunds do often become used to refer to physical objects/results of actions: "writing", "reading" (e.g. readings for a class), "drawing", "booking" (of a ticket), "crossing" (on a road), "wiring", "etching", and others. Using "working" to refer to the written steps of working out a maths problem is just another example in that vein.