This is from Brutal SC document -

The ancient Romans piped hot water through the walls and under the floors so as to warm up the rooms.
A. so as to warm up the rooms
B. and so would be able to warm up the rooms
C. to warm the rooms up
D. so that they could warm up the rooms
E. in order that they would warm up the rooms

OA is given as D.

Instructors, I am giving my exam in a week. Can you please explain when to use so that/so as to/ to. I am always confused.

I picked A because I have seen GMAC use 'so as to' in other questions.
Also, which is correct - warm up the rooms or warm the rooms up?

Hi, This is really an important trick of GMAT.

so as to : we need a verb after this.
so that : we need a subject after this, or u can say that a clause after so that.

now when you use "so as to", make sure there is only one AGENT before so as to.

here,
The ancient [Romans] piped hot water through [the walls] and under [the floors] so as to warm up the rooms

Can you see here we have 4 agents
romans
walls
floors
walls and floors

so This creates AMBIGUITY.

Best replacement of 'so as to' is 'so that'.
CLAUSE_1 so that CLAUSE_2
subject of CLAUSE_1 is subject of CLAUSE_2
so in ur question, "they" refers to Romans.

Its clear and the answer.
I hope it helps.

example:
I study a lot so as to score high on GMAT.
only one AGENT here, "I"

I study a lot so that I can score high on GMAT.

this question is horrible. you should run away from this source as fast as you can. don't look back.

you could argue for any one of (a), (c), or (d) here. all are acceptable.
if this were an official problem, it would say something like "in order to warm the rooms".

_________________
Being well-dressed gives a feeling of inward tranquillity [that] religion is powerless to bestow.
C.F. Forbes

Ron,

thank god this question is on this forum. i've had a lot of headache with the brutal 70 questions. in any case,

1. can i ignore what sunnyJain said? he mentioned about the ambiguity when using so as to?

2. you mentioned C would be ok.

C. to warm the rooms up
wouldn't the adverb "up" need to come after "warm"?
i was thinking of the example, "that room is up", which proved to me it must be an adverb not an adj.

please take Ron's advice and do not pay any more attention to this question..

_________________
Tim Sanders
Manhattan GMAT Instructor