GMAT Prep Test Math doubts

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by macattack » Tue Aug 06, 2013 4:11 am
For the DS question:
Each statement alone is clearly insufficient.
Taking the combined statement:
Case 1: p=10 and n= 6--->(10+6)(10-6) 16:5 R=1 and 4:3 R=1 and (16*4):15 R=4
Case 2: p=5 and n=1--->(5+1)(5-1) 6:5 R=1 and 4:3 R=1 and (6*4):15 R=9

Since we can get different answers we should choose E.

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by macattack » Tue Aug 06, 2013 4:24 am
Now for the geometry problem here is how it goes:
Step 1: calculate the radius of the circle--->R=sqrt((sqrt(3)^2)+1^2)=2
Step 2: Calculate the legth of the hypotenuse of the isosceles right triangle= R*sqrt(2)=2sqrt(2)

Now set up the equations:
Equation 1: s^2+t^2=4 (pythagorean theorem)
Equation 2: sqrt((s+sqrt(3))^2+(t-1)^2)=2sqrt(2) (distance between P and Q = legth of hypotenuse)

Step 3: square Equation 2:
(s+sqrt(3))^2+(t-1)^2=8
s^2+t^2+3+1+2sqrt(3)s-2t=8

Step 4: substitute equation one into equation 2 (s^2+t^2=4)
--->2sqrt(3)s-2t=0

Step 5: Rearrange the terms: t=sqrt(3)*s

Step 6: Plug the possible answer choice and check which one verifies s^2+t^2=4
The only possible answer is 1!
Hope that helped

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by Brent@GMATPrepNow » Tue Aug 06, 2013 6:11 am
Note: When posting questions, please use the spoiler function to hide the correct answer. This will allow others to attempt the question without seeing the final answer.


Here's my solution to the geometry question.
Image
So, as you can see s = 1, so the answer is B

Cheers,
Brent
Brent Hanneson - Creator of GMATPrepNow.com
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by gulshank1 » Tue Aug 06, 2013 6:15 am
Thanks!!

I will make sure the answers are hidden next time.

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by macattack » Tue Aug 06, 2013 7:37 am
Hi Brent would like to know if my method is correct? THanks