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Question on probability

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by [email protected] » Mon Dec 19, 2016 8:01 pm
Hi Sucheta,

When posting a GMAT question, you should make sure to post the ENTIRE prompt (including the 5 answer choices). Sometimes the answers are written in such a way so that you can avoid some of the 'work' (and/or avoid the long-winded 'math' approach). Without having the answer choices as a reference, we're forced to the math...

As it stands, this prompt is a bit vague; the number of rolls WILL impact the probabilities involved.

IF... there are 3 rolls, then the probability of rolling AT LEAST one 6 can be calculated by subtracting the probability of rolling NO 6s from 1...

1 - (5/6)(5/6)(5/6) = 1 - 125/216 = 91/216

However, IF... there are 4 rolls, then probability changes...

1 - (5/6)(5/6)(5/6)(5/6) = 1 - 625/1296 = 671/1296

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Rich
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by DavidG@VeritasPrep » Thu Dec 22, 2016 11:46 am
[email protected] wrote:Request you to please help me with the answer to the following:

A die is rolled n times, where n is at least 3. What is the probability that at least one of the throws yields a six.


Thank you
Sucheta
For a concrete example of a similar question with answer choices, see here: https://www.beatthegmat.com/probability- ... 08134.html
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