lichting wrote:
mikemcgarryHi, I'm totally convinced that B is right answer.
Just want to ask further.
What if statement 1 gives the slope of line OP (eg: 2), can statement 1 alone also sufficient?
Thank you so much in advance
Dear
lichting,
I'm happy to respond.
From the prompt information, we only know one angle in the triangle, angle P. (We don't explicitly have the value of that angle, but with the slope information and trigonometry--beyond what the GMAT expects you to know, we could find that angle. As it happens, that angle is 143°7'48.368", but you don't need to know how to find that.) The point is, from the fact that the slopes of OP and PQ are determined and fixed, angle P is locked into place at a specific value. All we know from the prompt is that one angle.
As it is, Statement #1 gives us only a length--thus, for triangle OPQ we have one length and one angle, and we can't find anything from that combination.
Now, your question is confusing to me. You see, in any GMAT DS questions, 100% of the time, the information in the prompt alone, without the statements, is always always always insufficient. We can never give a definitive answer to the DS prompt question solely from information in the prompt--the statements may or may not provide sufficient information, but without the additional information in the statements, we never can get anywhere. Thus, any information already present in the prompt never gets us any closer to sufficiency. If the information we have at any point is not sufficient, then repeating any part of it does absolutely zilch for us. This is a very common human misunderstanding that advertising and politicians like to exploit: repeating something doesn't actually make it more true. Thus, repeating the slope of OP, which we already know, does't absolutely zero to enhance the sufficiency of statement #1.
Let's say the question were different, and the prompt were asking for, say, the length of PQ.
Then, if statement #1 told the length of OP and
the slope of OQ, then from all three slope, we could find all the angles in the triangle, and with the value of the length, we could find all three sides. When I say "we could find them"--they are mathematical fixed with definite values as a result of that information, although finding the actual numerical lengths and angles would involve using trigonometry--again, beyond what the GMAT expects. Actually, this wouldn't be a real GMAT DS question, because the GMAT is scrupulous about not asking you to determine the sufficiency of quantities that are technically mathematically fixed, although the math to find them is beyond GMAT math: the GMAT DS never goes into that territory.
You may find this blog article relevant:
GMAT Data Sufficiency: Congruence RulesDoes all this make sense?
Mike
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Mike McGarry
Magoosh Test PrepEducation is not the filling of a pail, but the lighting of a fire. — William Butler Yeats (1865 – 1939)