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100 points for $49 worth of Veritas practice GMATs FREE VERITAS PRACTICE GMAT EXAMS Earn 10 Points Per Post Earn 10 Points Per Thanks Earn 10 Points Per Upvote ## There is a total of 120 marbles in a box, each of which is tagged by: AAPL ##### This topic has 3 expert replies and 0 member replies ### Top Member ## There is a total of 120 marbles in a box, each of which is ## Timer 00:00 ## Your Answer A B C D E ## Global Stats Difficult GMAT Paper Tests There is a total of 120 marbles in a box, each of which is red, green, blue, or white. If one marble is drawn from the box at random, the probability that it will be white is 1/4 and the probability that it will be green is 1/3. What is the probability that the marble will be either red or blue? A. 1/6 B. 1/4 C. 2/7 D. 1/3 E. 5/12 OA E ### GMAT/MBA Expert GMAT Instructor Joined 08 Dec 2008 Posted: 12540 messages Followed by: 1245 members Upvotes: 5254 GMAT Score: 770 AAPL wrote: GMAT Paper Tests There is a total of 120 marbles in a box, each of which is red, green, blue, or white. If one marble is drawn from the box at random, the probability that it will be white is 1/4 and the probability that it will be green is 1/3. What is the probability that the marble will be either red or blue? A. 1/6 B. 1/4 C. 2/7 D. 1/3 E. 5/12 OA E ...the probability that it [the marble] will be white is 1/4 So, 1/4 of the 120 marbles are white. In other words, there are 30 white marbles. ...the probability that it [the marble] will be green is 1/3 So, 1/3 of the 120 marbles are green . In other words, there are 40 green marbles. Altogether, there are 70 marbles that are EITHER white or green. This means that the remaining 50 marbles are EITHER red or blue. So, P(selected marble is EITHER red or blue) = 50/120 = 5/12 Answer: E Cheers, Brent _________________ Brent Hanneson â€“ Creator of GMATPrepNow.com Use our video course along with Sign up for our free Question of the Day emails And check out all of our free resources GMAT Prep Now's comprehensive video course can be used in conjunction with Beat The GMATâ€™s FREE 60-Day Study Guide and reach your target score in 2 months! ### GMAT/MBA Expert GMAT Instructor Joined 09 Oct 2010 Posted: 1114 messages Followed by: 29 members Upvotes: 59 AAPL wrote: GMAT Paper Tests There is a total of 120 marbles in a box, each of which is red, green, blue, or white. If one marble is drawn from the box at random, the probability that it will be white is 1/4 and the probability that it will be green is 1/3. What is the probability that the marble will be either red or blue? A. 1/6 B. 1/4 C. 2/7 D. 1/3 E. 5/12 $$? = {{\# \left( {{\rm{red}}\,\,{\rm{or}}\,\,{\rm{blue}}} \right)} \over {\,120\,\,{\rm{equiprobables}}\,}}$$ $$\# \left( {{\rm{red}}\,\,{\rm{or}}\,\,{\rm{blue}}} \right)\,\,\, = \,\,\,120\,\, - \,\,\# \left( {{\rm{white}}\,\,{\rm{or}}\,\,{\rm{green}}} \right) = 120 - \left[ {{1 \over 4}\left( {120} \right) + {1 \over 3}\left( {120} \right)} \right] = 50$$ $$? = {5 \over {12}}$$ This solution follows the notations and rationale taught in the GMATH method. Regards, Fabio. _________________ Fabio Skilnik :: GMATH method creator ( Math for the GMAT) English-speakers :: https://www.gmath.net Portuguese-speakers :: https://www.gmath.com.br ### GMAT/MBA Expert GMAT Instructor Joined 25 Apr 2015 Posted: 1808 messages Followed by: 14 members Upvotes: 43 AAPL wrote: GMAT Paper Tests There is a total of 120 marbles in a box, each of which is red, green, blue, or white. If one marble is drawn from the box at random, the probability that it will be white is 1/4 and the probability that it will be green is 1/3. What is the probability that the marble will be either red or blue? A. 1/6 B. 1/4 C. 2/7 D. 1/3 E. 5/12 We see that there are 120 x 1/4 = 30 white marbles and 120 x 1/3 = 40 white marbles, so there must be 120 - 70 = 50 blue or red marbles. So the probability of selecting either a red or blue marble is 50/120 = 5/12. Alternate solution: Since P(red) + P(green) + P(blue) + P(white) = 1 and P(green) = 1/3 and P(white) = 1/4, we have: P(red) + 1/3 + P(blue) + 1/4 = 1 P(red) + P(blue) = 1 - 1/3 - 1/4 P(red or blue) = 5/12 Answer: E _________________ Scott Woodbury-Stewart Founder and CEO • 5-Day Free Trial 5-day free, full-access trial TTP Quant Available with Beat the GMAT members only code • Free Practice Test & Review How would you score if you took the GMAT Available with Beat the GMAT members only code • FREE GMAT Exam Know how you'd score today for$0

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