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Re: a couple from the gmat prep I took today [#permalink]
08 Nov 2009, 01:27

for the second question, the only trick is in making sense of the convoluted language in the question stem. took me a minute to make sense of all the decrease... 10%, before and after july 1..... jumble.

After that, the actual calculation takes very little time regardless of the method used (algebra / number substitution).

Re: a couple from the gmat prep I took today [#permalink]
08 Nov 2009, 05:01

The semicircle one was really dodgy. hgp2k, nice solution and with abhi758, amazed @ ur speeds great going! saruba, if you don't mind my asking, how much was the quant score for this prep test? wondering if it is a 750 level Q

Re: a couple from the gmat prep I took today [#permalink]
08 Nov 2009, 06:54

The semicircle problem;

If we draw a perpendicular line through the point P to x axis at point A (-sqrt[3], 0), we have POA as 30-60-90 Triangle, where PA=2; PA =1; AO=sqrt[3]

Similarly we draw a perpendicular line through the point Q to x axis at point B; we have QOB as 60-30-90 Triangle , where OB =1; QB=sqrt[3]; OQ=2 (Since POQ is right angle triangle)

Re: a couple from the gmat prep I took today [#permalink]
19 May 2011, 10:05

Solving for the semi-circle problem. I used trignometry to solve the problem. We know that x^2+y^2= 3+1=4, therefore the radii OP is 2.

This radii OP is the hypotenuse for the right triangle formed by height 1 and sqrt3. solving for the exterior angle i.e. POX. Using sine theta formula: Sine theta = opp/hyp = 1/2. Therefore the angle is 30. once you know this angle is 30, then the angle QOX on the other side is 60.

Now the radii OQ is 2. Cos theta = Adj side/hyp Cos 60 = s/2 s = 1, since cos 60 is 1/2
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