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Probability- GPrep 4

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by prachi18oct » Fri Oct 10, 2014 4:30 am
Don't remember exactly the words but the question was like this :-

Probability that prices of Stock A will keep on increasing is 0.54 and probability that prices of STock B will keep on increasing is 0.68. What is the probability that neither of these happen?

My solution:-

P(A not happens) = 1-0.54 = 0.46
P(B not happens) = 1-0.68 = 0.32
P(A and B not happen) = 0.46 * .32 = 0.14

OA 0.32

Please explain
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by Brent@GMATPrepNow » Fri Oct 10, 2014 9:31 am
prachi18oct wrote:Don't remember exactly the words but the question was like this :-

Probability that prices of Stock A will keep on increasing is 0.54 and probability that prices of STock B will keep on increasing is 0.68. What is the probability that neither of these happen?

My solution:-

P(A not happens) = 1-0.54 = 0.46
P(B not happens) = 1-0.68 = 0.32
P(A and B not happen) = 0.46 * .32 = 0.14

OA 0.32

Please explain
Please take the time to properly transcribe the question (you are missing some key words)) AND provide the 5 answer choices.

Once you've done that, you will likely get a response.

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by prachi18oct » Fri Oct 10, 2014 9:42 am
This was a GMATPrep 4 question which I don't have with me currently. If not the solution of this problem, Can you please explain if this is the correct way of solving it.
P(A) = x
P(B) = y
Probability that neither A or B occurs is (1-x)(1-y)
?
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by Brent@GMATPrepNow » Fri Oct 10, 2014 9:46 am
Here's the original question:
If the probability is 0.54 that stock A will increase in value during the next month and the probability is 0.68 that stock B will increase in value during the next month, what is the greatest possible value for the probability that neither of these 2 events will occur?
A) 0.22
B) 0.32
C) 0.37
D) 0.46
E) 0.63
Here's Mitch's great reply: https://www.beatthegmat.com/gmat-prep-ex ... 72553.html


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by prachi18oct » Fri Oct 10, 2014 10:20 am
Hi Brent,

How can we assume that the increases in stock prices of A and B are dependent events like buying lottery and winning lottery events?
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by [email protected] » Fri Oct 10, 2014 10:37 am
Hi prachi18oct,

In this prompt, we have to assume that the two events are dependent because the question asks for the GREATEST POSSIBLE probability that neither of the 2 events would occur. When the question varies from the "normal" version, you have to be ready to adjust your thinking (and often, how you do the math).

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