As a rule, please note:
If units are not provided in any question on the GMAT (and you will see questions where this is the case), assume them to be consistent. For example, in statement (1) here, assume the units of the volume to be m^3 (or cm^3 or mm^3) and the units for the surface area to be m^2 (or cm^2 or mm^2) as the case may be.
One some number properties questions, you will find that numbers are often not specified as being integers, whole numbers, natural numbers etc. For example, a sample DS question could be:
What is x?
(1) x^2 = 34
In this case, nothing is said about x (whether it an integer, whole number etc). Make no assumptions about x, except that it is real (i.e. assume it can be fractional, negative, positive, zero).
Free profile evaluation by top b-school alumni: email us at firstname.lastname@example.org
B-school application service http://www.gyanone.com/appone.html
Visit our blog: http://www.gyanone.com/blog