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What's the source of this question? I can't imagine a gmat question testing a somewhat esoteric formula without another way of doing this. Also, r,s>0 suggests that there's another way of doing this problem if you don't know that formula. Anyone know another approach? For almost every DS question, ...

by tailoc

Sat Oct 08, 2011 7:54 am
Forum: Data Sufficiency
Topic: Coord Geo
Replies: 18
Views: 10393

Formula: Ra+Rb=Rx
<=> 1/(a+x) + 1/(b+x) = 1/x
=> x = sqrt(ab)

by tailoc

Wed Sep 28, 2011 5:54 am
Forum: Problem Solving
Topic: more than x minutes
Replies: 22
Views: 10924

Say a,b,c : price of each items a>b>c
from stem: 20%a+10%(b+c)>15%(a+b+c) ??? or a>b+c ???
statement 1: a=50 b=20, with c which is smaller than or equal b => always a>b+c sufficient
statement 2: clearly insufficient

OA: A

by tailoc

Tue Sep 27, 2011 12:51 am
Forum: Data Sufficiency
Topic: Henry purchase 3 items during a sale
Replies: 17
Views: 14410

I used formula: sum of consecutive even integers = [(last even integer + first even integer)/2]*[(last even integer - first even integer)/2 +1] n is last odd integer in set =>n-1 is last even integer in set 2 is first even integer in set So (n-1+2)/2 * [(n-1-2)/2 +1] = 78*79 (n+1)/2 * [(n-3)/2 +1]= ...

by tailoc

Tue Sep 20, 2011 11:46 pm
Forum: Problem Solving
Topic: Difficult Math Question #1
Replies: 30
Views: 26936
by tailoc

Tue Sep 20, 2011 11:42 pm
Forum: GMAT Math
Topic: Difficult GMAT Math Problems
Replies: 34
Views: 130679

6 prizes is different.

First one can win any a prize of 6 prizes ---> 6 ways
Second one can win any a prize of 5 prizes remaining ---> 5 ways
Likewise, third one --->4 ways, and fourth one ---> 3 ways
So, 6*5*4*3 = 360 ways

by tailoc

Mon Sep 19, 2011 10:39 am
Forum: Problem Solving
Topic: combination
Replies: 5
Views: 1065

OA is D
Say that t is day when 5 workers leave
Say that number of units 20workers perform are 600 units.
=> rate = 600/30=20units/20workers=1unit/worker.
So,
Equation: q=r*t
20*1*t + 15*1*(35-t)=600
t=15 days

by tailoc

Wed Sep 14, 2011 12:10 am
Forum: Problem Solving
Topic: WORK & TIME
Replies: 6
Views: 9318

I think that in order to answer this question. We should understand method of reasoning in stimulus. Initially, author mentioned that researchers concluded "few" of extinction. After that author used a contradiction "however". Finally, author used some details to show that extinc...

by tailoc

Fri Sep 09, 2011 1:53 am
Forum: Critical Reasoning
Topic: Inference doubt
Replies: 20
Views: 11224

A is correct. The length of train is: T___N The length of platform is : P_______M At beginning: N travel from P to M = length of platform However, in order to train cross platform <=> T at M =the distance between N and T = length of train. So, train cross platform = length of platform + length of tr...

by tailoc

Wed Sep 07, 2011 9:45 pm
Forum: Problem Solving
Topic: What is the length of the platform in meters...............
Replies: 46
Views: 27428

I think that answer A is 50%, A seems to be an assumption rather than strengthen argument. However, D only mentioned reducing wage that will lead to the resignation of some labors. This do not mean that layoffs damage morale less. Therefore, choose A is a correct answer.

by tailoc

Mon Sep 05, 2011 1:17 am
Forum: Critical Reasoning
Topic: CR Strengthen: Employee morale
Replies: 27
Views: 13882

B is incorrect. It did not attack argument, however it seems to be a illustration of premise which is mentioned in argument.

C is correct because if safety is only a criteria to judge an appliance to be acceptable as "standard"

by tailoc

Wed Aug 31, 2011 1:06 am
Forum: Critical Reasoning
Topic: Microwave
Replies: 25
Views: 13937

when I read the question, I saw a problem in the question "The amount of money which Tom paid more than what Harry paid is " with 100:60:409. plz correct question

by tailoc

Tue Aug 30, 2011 9:31 am
Forum: Problem Solving
Topic: Tom,Dick and Harry
Replies: 23
Views: 29447

My answer: X is the weight of water that was evaporated Before evaporation: 100 pounds of cucumbers ---- 99 pounds of water After evaporation : 100-X pounds of cucumbers ---- 99-X pounds of water So (99-X)/(100-X)=0.98 <=> 1=0.02X => X=50 => new weight of cucumbers = 100 - 50 = 50

by tailoc

Wed Aug 24, 2011 1:34 am
Forum: Problem Solving
Topic: Cucumber
Replies: 26
Views: 20380

First, eliminate B and D ,"New Mexico site where first discovered in 1932" is wrong because Clovis points were discovered in 1932.

finally, eliminate C and E because of wrong tense (have been discovered in 1932). Also E is not concision.

Answer is A

by tailoc

Wed Aug 17, 2011 1:13 am
Forum: Sentence Correction
Topic: Multiple modifiers
Replies: 30
Views: 17058

If x>0, then is x^3-3x^2+2x divisible by 4? 1. x=4y+4 where y is an integer 2. x=2z+2; were z is an integer I saw this quesiton in Manhattan guide, but i am not convinced with its answer. statement 1: x=4(y+1) => x^3 ,x^2, 2x divisible by 4 with any integers of y statement 2: x=2(z+1) => x^3 ,x^2, ...

by tailoc

Mon Jul 25, 2011 3:14 am
Forum: Data Sufficiency
Topic: Interesting DS question
Replies: 49
Views: 22411