GMAT Problem Solving Discussions

[cyndrella]

Originally Posted by dumbJoe

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

[sharkon]

Originally Posted by cyndrella

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

[Sriram_Avadhani]

Originally Posted by cyndrella

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

[cyndrella]

Originally Posted by sharkon

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

[ajayreddy]

Originally Posted by cyndrella

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?

[sharkon]

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

[cyndrella]

try this....




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

[dumbJoe]

Originally Posted by cyndrella

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

[cyndrella]

Originally Posted by dumbJoe

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

[abhijit]

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.