What is the total surface area of rectangular solid R?

[sharmin.karim]

What is the total surface area of rectangular solid R?

1) The surface area of one of the faces of R is 48
2) The length of one of the edges of R is 3

[agha79]

Please post the OA:

IMO answer is "E"

[vishalsahdev03]

IMO "E"

what is OA ?

[Ben Ku]

Hi Sharmin,

Is there a picture that accompanies this problem? If not, then the answer is (E) since we are not given any dimensions. Although (1) gives the surface area for one face, (2) gives the length of an edge which may or may not be on the face given in (1).

Please also describe a bit where you got stuck or confused. This way we can provide the most helpful response.

[bhumika.k.shah]

No diagram is given with this Q.
Source : GMAT prep

[Ben Ku]

Then my response stands. If there's a particular part in this problem that you don't get, then please post!

[pranjali.deshpande]

Hi Ben,




1. if the area of the face is 48 and the edge having length 3 is one of the faces then 3x =48 and x= 16. But we are still missing one of the edges right?


but of course, the above question does not say that edge having length 3 is one of the edges of the side having an area of 48.

[RonPurewal]

Hi Ben,




1. if the area of the face is 48 and the edge having length 3 is one of the faces then 3x =48 and x= 16. But we are still missing one of the edges right?


but of course, the above question does not say that edge having length 3 is one of the edges of the side having an area of 48.

no, the problem doesn't specify which edge you are talking about; you are correct in asserting that the edge of length 3 could either (a) be one of the sides of the face whose area is 48, or (b) the one of the sides of one of the other faces.

however, all that is beside the point -- just the case you considered in your first paragraph, alone, already proves that the statement is insufficient!
i.e., that case leaves us with a situation in which one dimension of the solid is completely undetermined, even if we have both of the statements. therefore, the answer is (e).
takeaway:
once you prove that a statement is insufficient, there is no need to consider further cases of that statement.