Search found 27 matches
musicdaemon wrote:Case I:
for, x^3 (1 - x^2) <0>1[/b]
i.e. x^2-1>0 ...................... this condition is not supplied in the question
MODS,
There is some problem in formatting of this part, not able to paste it properly.
anyway case 2 suffices my explanation
- by musicdaemon
Fri Apr 04, 2008 8:42 pm- Forum: Data Sufficiency
- Topic: OG Page 290, # 154 - need faster method
- Replies: 5
- Views: 1766
Case I:
for, x^3 (1 - x^2) <0>1[/b]
i.e. x^2-1>0 ...................... this condition is not supplied in the question
- by musicdaemon
Fri Apr 04, 2008 8:41 pm- Forum: Data Sufficiency
- Topic: OG Page 290, # 154 - need faster method
- Replies: 5
- Views: 1766
Analyse the first option: Case I: x^3 (1 - x^2) <0>1 i.e. x^2-1>0 ...................... this condition is not supplied in the question Case II: x^3 = -ve, then (1-x^2) must be +ve The necessary and sufficient condition for (1-x^2) to be +ve, is x^2<1 i.e x^2-1<0 .......... Which is the conditon sup...
- by musicdaemon
Fri Apr 04, 2008 8:27 pm- Forum: Data Sufficiency
- Topic: OG Page 290, # 154 - need faster method
- Replies: 5
- Views: 1766
guys, how do you come up with: male death = 9 Female death rate = 21 Its says 30% of the dead mice are male and 70% female. How do you know what x is, x being the number of dead mice? I get the solution via the equation but not he number picking ,spefically for the deadmice, i get the initall 100 =...
- by musicdaemon
Tue Apr 01, 2008 9:31 am- Forum: Problem Solving
- Topic: Rats Rats Rats
- Replies: 9
- Views: 2490
Re: hmm
Do you have any pointers musicdaemon? How do you not miss key informaiton? I guess my thought process converts all the words into equations. Here is I do it 1. work backwards , convert the final question in mathematical form, for this question: what was the ratio of the death rate among the male ra...
- by musicdaemon
Tue Apr 01, 2008 9:26 am- Forum: Problem Solving
- Topic: Rats Rats Rats
- Replies: 9
- Views: 2490
Re: fun question
FIRST OFF; 30 dead rat population and = 9 male and 21 female so : 9 male : 21 female simplified to 3/7 This is the same thing as musicaemon but I looooove smart numbers! > [/b] Engin, Question asks -> what was the ratio of the death rate among the male rats to the death rate among the female rats? ...
- by musicdaemon
Mon Mar 31, 2008 12:07 am- Forum: Problem Solving
- Topic: Rats Rats Rats
- Replies: 9
- Views: 2490
- by musicdaemon
Thu Mar 27, 2008 8:46 pm- Forum: Problem Solving
- Topic: exponenets
- Replies: 6
- Views: 2001
- by musicdaemon
Thu Mar 27, 2008 10:38 am- Forum: Problem Solving
- Topic: PS OG #138
- Replies: 2
- Views: 1792
Let there be total 100 rats. Then, according to question Male Rats = 40 Female Rats = 100- male rats = 100-40 = 60 Suppose, total number of dead rats = x therefore, No. of dead male rats = (30/100)x= 0.3x No. of dead female rats = x-0.3x = 0.7x Death rate = (Dead rats)/(no. of rats to begin with) Ma...
- by musicdaemon
Thu Mar 27, 2008 10:22 am- Forum: Problem Solving
- Topic: Rats Rats Rats
- Replies: 9
- Views: 2490
Question asks -> what is the time for the cylinder to fill from empty to half full, So, height in this case should be 10 and not 20 ( I think you made this mistake, that is why you get 980) Thus volume = pi*(r^2)*h = pi*(7^2)*10 = 490pi cubic meters Time Req = volume/Rate = (490pi)/pi = 490 min Rega...
- by musicdaemon
Tue Mar 25, 2008 10:55 pm- Forum: Problem Solving
- Topic: manhattan geometry rate problem
- Replies: 3
- Views: 3107
Total No. of songs = 12 Total no. of times each song is selected = 4 Therefore, total number of song selections = 12*4=48 Since, only 2 selections are allowed per student Number of students = (total number of song selections/selections allowed per student) = 48/2 = 24 .................... Ans!!! wha...
- by musicdaemon
Tue Mar 25, 2008 9:40 am- Forum: Problem Solving
- Topic: GMAT PREP!!!
- Replies: 1
- Views: 1564
i also think the ans is copied wrong, i used the combinatorics to solve, at least 1 black & white set is to be selected, i.e either one or both the sets are B&W. Suppose, case is to select none of the B&W sets, n(E)= number of events of two color sets being selected = 6C2 = 15 n(S)= numb...
- by musicdaemon
Fri Mar 21, 2008 10:45 am- Forum: Problem Solving
- Topic: Probability
- Replies: 4
- Views: 4339
useful trick
A useful Trick: i use it often to find the range of integer values of a linear equation in two variables for example, in the solution for this question, the equation 3x+2y=15 , gives x=(15-2y)/3, now go on putting y=0,1,2,3 ..... since, x is to be an integer, (15-2y) must always be a multiple of 3 t...
- by musicdaemon
Fri Mar 21, 2008 10:30 am- Forum: Problem Solving
- Topic: Ratios: Bag A contains red, white and blue marbles such that
- Replies: 7
- Views: 9456
For Bag A: R:W = 1:3 = 2:6 W:B=2:3=6:9 Thus, R:W:B= 2:6:9 If x be the common factor for this proportion , then number of balls in bag A = 2x+6x+9x …………………..(1) For bag B: R:W = 1:4 If y be the common factor for this proportion, then number of balls in bag B = y+4y…………………………(2) Give, Total no. of whi...
- by musicdaemon
Fri Mar 21, 2008 2:02 am- Forum: Problem Solving
- Topic: Ratios: Bag A contains red, white and blue marbles such that
- Replies: 7
- Views: 9456
Given x^2+y^2+z^2=75………………………… (1) Suppose, x+y+z = k…………………………………(2) Now, we know from the standard formula x^2+y^2+z^2 +2(xy+yz+zx) = (x+y+z)^2 Putting the values from (1) & (2) =>75+2(xy+yz+zx) = k^2 => xy+yz+zx = (k^2 -75)/2 ………..(3) Since, x,y and z are all integers, therefore, (k^2 -75)/2 ...
- by musicdaemon
Tue Mar 18, 2008 8:29 pm- Forum: Problem Solving
- Topic: GMAT PREP?
- Replies: 8
- Views: 7999