GMAT Prep Toughie

Question

hello,, find attached doc which has 3 gmat prep questions. i got all of them wrong

would appreciate any discussion on teh questions. regards, NEo

GMBA85 · Answer

could you provide the OA?

Neochronic · Answer

I would have liked to have some discussion first and then post the OA.
 
Anyways, heres the OA .. B,B,A in order.

Please do post your explanations.

greenoak · Answer

Nice questions!

For the first:
Let P = number of houses with patio, SP – number of houses with swimming pool. Total n of houses = P + SP – (P and SP) + (neither P nor SP). (1) is clearly insuff. From (2) we know that the last two cancel off. So we can obtain SP, and (2) is suff.

For the second:
The trick here is that we don’t know whether k is positive or negative. However, we don’t have to know this in order to answer. From (2): Since a8 is in the middle of the sequence, there are 7 numbers on either side, and so exactly 7 will be greater than 10 (though we still can’t say whether they are to the left of a8 or to the right). So (2) is suff.

greenoak · Answer

About third – I remember it well; it’s from OG11 # 206. I will try to explain it without the drawing

Let A be the center of the circle. Then draw AP and AQ. The main task is to calculate the central angle PAQ. Let’s note that AP=AR. So, angle APR=angle ORP=35. Then, angle QPR = angle ORP as well (since PQ||OR). So, the central angle equals 180-(2*2*35) = 40. Then, 40 is 1/9 of 360, that is, 40 = 2pi/9. Radius of the circle is 18/2=9. So, the answer is 9*2pi/9 = 2pi.

FN · Answer

OK..

here is how did them

Total House=Patio+SwimmingPool-Both+Neither

75=P+S-Both+neither

1) says 38 have just patio.. OK..so P=38..then it means both would have 10.. however we dont know about neither..so Insuff

2) 75=48+S-X+X

S=75-48 Sufficient

2 Question
an= An-1 + K; 2<=n<=15

1)A1=24..

OK so I dont know anything about K..Insuff

2)
A8=10..

A8=A1+7K=10.. if A1+7K=10..then

A7=A1+6K=A8-K

A9=A1+8K=A8+K
I am told that K is a non-zero constant..so if A8=10..then A7 i.e 10-K will be less than 10..and so on..

A9+K will be 10+K..and so will be bigger than 10..

B is sufficient!

If I assume K is negative then A7>A8...however same number will be greater than A8...

as a8 is the median of the sequence

3) other posters have given a good explanation.. ans is 2pi

a2..a8...a15

Neochronic · Answer

thanks GreenOak for the answers.
The explanations were brilliant.

regards,
Neo

kykboxr · Answer

Indeed. Kudos to all.

GMAT Prep Toughie

Prep Toolkit

Top 5 GMAT Debrief Videos

615 to 715 in 15 Days (Ria's Strategies)

More than Quant/Verbal Abilities: Speed vs. Accuracy

745 with Only Self-Prep and GMAT Club

From 555 to 765: 210-point Improvement

Perfect 805 Score Debrief by Julia

My Rewards