GMAT Prep Test Math doubts

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gulshank1: Newbie | Next Rank: 10 Posts; Posts: 4; Joined: Tue Dec 27, 2011 7:21 am

by gulshank1 » Tue Aug 06, 2013 1:57 am

Hi,
I am unable to arrive at the correct answers for the 2 questions attached. The correct answers are highlighted.

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Source: Beat The GMAT — Problem Solving | Tue Aug 06, 2013 1:57 am

macattack: Senior | Next Rank: 100 Posts; Posts: 90; Joined: Wed Jun 26, 2013 10:55 pmFollowed by: 1 member; Thanked: 11 times

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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macattack: Senior | Next Rank: 100 Posts; Posts: 90; Joined: Wed Jun 26, 2013 10:55 pmFollowed by: 1 member; Thanked: 11 times

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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GMAT/MBA Expert

Brent@GMATPrepNow: GMAT Instructor; Posts: 16207; Joined: Mon Dec 08, 2008 6:26 pmFollowed by: 1268 members; Location: Vancouver, BC; Thanked: 5254 times; GMAT Score:770

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.

So, as you can see s = 1, so the answer is B

Cheers,
Brent

Brent Hanneson - Creator of GMATPrepNow.com

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gulshank1: Newbie | Next Rank: 10 Posts; Posts: 4; Joined: Tue Dec 27, 2011 7:21 am

by gulshank1 » Tue Aug 06, 2013 6:15 am

Thanks!!

I will make sure the answers are hidden next time.

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macattack: Senior | Next Rank: 100 Posts; Posts: 90; Joined: Wed Jun 26, 2013 10:55 pmFollowed by: 1 member; Thanked: 11 times

by macattack » Tue Aug 06, 2013 7:37 am

Hi Brent would like to know if my method is correct? THanks

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