GMAT Problem Solving Discussions

MBA
522
since the flowers must come from the rest 6, we only need to consider that case
6c2, total possibilities being 8c2. here for all practical purposes we can take them to be distinct, because while calculating probability we are counting the cases altogether........but i dont see the answer 6c2/8c2 ie 15/28


I Feel this is correct dumbJoe..it should be 15/28
523
cyndrella Says
I Feel this is correct dumbJoe..it should be 15/28


I think the answer is 27/28
with ajay's explanation being correct.

Now coming to joe's answer
6c2/ 8c2 would mean prob of flowers being non tulips
but he did not consider when 1 of them is tulip and other non tulip

ie 2c1 * 6c1 /8c2 = 12/28

so total prob = 1= prob of 2 tulips + prob of 1 tulip + prob of no tulip
=1/28+12/28+15/28

I hope I was clear
524
cyndrella Says
I Feel this is correct dumbJoe..it should be 15/28

Flower shop: 2 tulips, 2 roses, 2 daisies, and 2 lillies. If 2 (two) are sold at random, what is the prob that both flowers are not tulips?

Hi Somebody answered .27/28 is correct . two explanantions
1. probability that both are not tulips= 1-probabilty both are tulips.

=1-2c2/8c2 = 1-1/28 = 27/28

2. Probability that both are not tulips = probabilityof exacltly 1 tulip+prabability of no tulip
=2c1*6c1/8c2 + 6c2/8c2
=2*6/28 + 15/28 = 27/28
525
I think the answer is 27/28
with ajay's explanation being correct.

Now coming to joe's answer
6c2/ 8c2 would mean prob of flowers being non tulips
but he did not consider when 1 of them is tulip and other non tulip

ie 2c1 * 6c1 /8c2 = 12/28

so total prob = 1= prob of 2 tulips + prob of 1 tulip + prob of no tulip
=1/28+12/28+15/28

I hope I was clear


well,when we consider 6c2/ 8c2,we are not considering the 2 tulips at all.So,the case of one tulip and other not is already eliminated.
Simply put..

Cases of both flowers being tulip = 1
Cases of one flower tulip and other not = 12
Total = 13 cases when at least one flower is tulip

Cases when none is tulip = 15

Prob=15/(13+15) = 15/28
Though the answer given was 27/28 from where i took this problem...that seems to be incorrect..further analysis is still welcome:)
526
well,when we consider 6c2/ 8c2,we are not considering the 2 tulips at all.So,the case of one tulip and other not is already eliminated.
Simply put..

Cases of both flowers being tulip = 1
Cases of one flower tulip and other not = 12
Total = 13 cases when at least one flower is tulip

Cases when none is tulip = 15

Prob=15/(13+15) = 15/28
Though the answer given was 27/28 from where i took this problem...that seems to be incorrect..further analysis is still welcome:)

well, read the sum..it only asks for the probability when BOTH ARE NOT tulips..so tht means, u hv to consider the probability when none of them are tulips + when one of them is a tulip..it seems u did not correctly interpret the question..15/28 wud hv been the correct answer when the question wud hv read as :
WHAT IS THE PROBABILITY THAT NONE OF THE FLOWERS ARE TULIPS?
527

I think enough time has been spent on this problem. Time to move on

528

try this....




1/33
2/33
1/3
16/33
11/12

529
try this....




1/33
2/33
1/3
16/33
11/12




ans is 6c4 x 2^4 / 12c4 ie 16/33
we need to have four different couples from which people come, and than for every couple we have 2 ways to pick people........and the total ways to pick four people are 12c4
530
ans is 6c4 x 2^4 / 12c4 ie 16/33
we need to have four different couples from which people come, and than for every couple we have 2 ways to pick people........and the total ways to pick four people are 12c4


perfect answer...16/33
531

Guys,
Need you help here. I have my Gmat on 29th, and gave GmatPrep1 today, scoring 720, with a 51 in Math. However, I got 3 problems wrong in Math, and since gmatprep does not provide explanations , can someone please explain the solution to the following problem (I've been struggling on this since an hour and now I'm fed up!!) -

Q. if xy=1, what is the value of 2(x+y)^2 / 2(x-y)^2 ?
A.
1. 2
2. 4
3. 8
4. 16
5. 32

Thanks in advance. 😃

532
Guys,
Need you help here. I have my Gmat on 29th, and gave GmatPrep1 today, scoring 720, with a 51 in Math. However, I got 3 problems wrong in Math, and since gmatprep does not provide explanations , can someone please explain the solution to the following problem (I've been struggling on this since an hour and now I'm fed up!!) -

Q. if xy=1, what is the value of 2(x+y)^2 / 2(x-y)^2 ?
A.
1. 2
2. 4
3. 8
4. 16
5. 32

Thanks in advance. :)


are you sure, you copied down the expression correctly?
substitution with x=2 and y= 1/2 should do
533

Yes.. I did.. I'd taken the same numbers during the test. Plugging in 2 and 1/2 evaluates to 25/9 right? Im sure that Im doing something very silly mistake here... Probably my stressed out brain has given up. :satisfie:
Can you please explain the solution?

534
Yes.. I did.. I'd taken the same numbers during the test. Plugging in 2 and 1/2 evaluates to 25/9 right? Im sure that Im doing something very silly mistake here... Probably my stressed out brain has given up. :satisfie:
Can you please explain the solution?

dude...with the present given data, u are never going to get an integer value as an answer because u are going to get two undivisible numbers in the numerator and denominator...so for the time being, leave this sum and post the remaining two tht u got wrong..
535

Ok.. here's the other one -

If M=(4)^1/2 + (4)^1/3 + (4)^1/4, then value of M is -

1. less than 3
2. equal to 3
3. between 3 and 4
4. equal to 4
5. greater than 4

I had to guess at this one since I had just 2 minutes left and 3 questions remaining :neutral: (and as always, most of my guesses are wrong ??:??: )

536
Ok.. here's the other one -

If M=(4)^1/2 + (4)^1/3 + (4)^1/4, then value of M is -

1. less than 3
2. equal to 3
3. between 3 and 4
4. equal to 4
5. greater than 4

I had to guess at this one since I had just 2 minutes left and 3 questions remaining :neutral: (and as always, most of my guesses are wrong ??:??: )

dude...see, 4^1/2 = 2 and 4^1/4 = 2^1/2 = 1.4142..so 4^1/3 must lie between 2 and 1.4142..thus, u can see the answer is definitely greater than 4...answer is E
537
Post 7
I think the answer should be E.


The answer to this one should be C according to me.

1. It will give you an expression in terms of G and B.. i.e. G+14/B=16/9 this would give you and expression like G+B=??.. So A is not possible and D is ruled out.
2. This would again give you an equation as the statement says that Girls are more than Boys...etc.etc... so it will again give you an equation in terms of G and B..

By combining both you will get a soln.
538
ajayreddy Says
dude...with the present given data, u are never going to get an integer value as an answer because u are going to get two undivisible numbers in the numerator and denominator...so for the time being, leave this sum and post the remaining two tht u got wrong..


Hi is the anwer 8. if that is the case question may be wrong. read / as -
539
ajayreddy Says
dude...see, 4^1/2 = 2 and 4^1/4 = 2^1/2 = 1.4142..so 4^1/3 must lie between 2 and 1.4142..thus, u can see the answer is definitely greater than 4...answer is E



Dude! How about this explanation:-

(4)^1/2 = -2
(4)^1/3 = 1.6 (Approx.)
(4)^1/4 = -(square root of 2) = -1.41 (approx.)

So equation = -2 + 1.6 - 1.4 = -1.8 (approx.)

So Answer should be (A); less than 3.

:)


Cheers,
Sumit
540
Dude! How about this explanation:-

(4)^1/2 = -2
(4)^1/3 = 1.6 (Approx.)
(4)^1/4 = -(square root of 2) = -1.41 (approx.)

So equation = -2 + 1.6 - 1.4 = -1.8 (approx.)

So Answer should be (A); less than 3.

:)


Cheers,
Sumit


Hi
(4)^1/2 cannot be equal to -2. similarly (4)^1/4 also cannot be a -ve number.
541
Hi
(4)^1/2 cannot be equal to -2. similarly (4)^1/4 also cannot be a -ve number.


Wow! Let me explain.

How about x^2 = 4
=> x = +2 or -2.

Let x = (y)^1/2

So y = +2 or -2.

square root of 4 can be +2 or -2; of course, because (2)^2 = (-2)^2 = 4.


Cheers,
Sumit