v-rap Posted April 1, 2008 Share Posted April 1, 2008 Hi, Below are some of the great probability problems for gmat. 1.There are 9 beads in a bag. 3 beads are red, 3 beads are blue, and 3 beads are black. If two beads are chosen at random, what is the probability that they are both blue? A. 1/81 B. 1/12 C. 2/9 D. 1/3 E. 1/4 2 A letter is randomly selected from the word Mississippi. What is the probability that the letter will be an s? A. 1/11 B. 3/10 C. 4/11 D. 1/4 E. 1/3 3. A certain deck of cards contains 2 blue cards, 2 red cards, 2 yellow cards, and 2 green cards. If two cards are randomly drawn from the deck, what is the probability that they will both are not blue? A. 15/28 B. 1/4 C. 9/16 D. 1/32 E. 1/16 4. A fair coin is tossed, and a fair six-sided die is rolled. What is the probability that the coin come up heads and the die will come up 1 or 2? A. 1/2 B. 1/4 C. 1/6 D. 1/12 E. 1/3 5. A bag of 10 marbles contains 3 red marbles and 7 blue marbles. If two marbles are selected at random, what is the probability that at least one marble is blue? A. 21/50 B. 3/13 C. 47/50 D. 14/15 E. 1/5 6. A fair, six-sided die is rolled. What is the probability that the number will be odd? A. 1/4 B. 1/2 C. 1/3 D. 1/6 E. 1/5 7. A letter is randomly select from the word studious. What is the probability that the letter be a U? A. 1/8 B. 1/4 C. 1/3 D. 1/2 E. 3/8 8. A bag contains 2 red beads, 2 blue beads, and 2 green beads. Sara randomly draws a bead from the bag, and then Victor randomly draws a bead from the bag. What is the probability that Sara will draw a red marble and Victor will draw a blue marble? A. 2/13 B. 1/5 C. 1/3 D. 1/10 E. 2/15 9. If two fair, six-sided dice are rolled, what is the probability that the sum of the numbers will be 5? A. 1/6 B. 1/4 C. 1/36 D. 1/18 E. 1/9 10. If four fair coins are tossed, what is the probability of all four coming up heads? A. 1/4 B. 1/6 C. 1/8 D. 1/16 E. 1/32 11. The probability that a certain event will occur is 5/9. What is the probability that the event will NOT occur? A. 5/9 B. 4/9 C. 2/9 D. 1/4 E. 1/2 12. A certain bag contains red, blue, yellow, and green marbles. If a marble is randomly drawn from the bag, the probability of drawing a blue marble is .2, the probability of drawing a red marble is .3, and the probability of drawing a yellow marble is .1. What is the probability of drawing a green marble? A. .5 B. .6 C. .2 D. .4 E. .3 13. A bag contains 3 red marbles, 3 blue marbles, and 3 green marbles. If a marble is randomly drawn from the bag and a fair, six-sided die is tossed, what is the probability of obtaining a red marble and a 6? A. 1/15 B. 1/6 C. 1/3 D. 1/4 E. 1/18 14. A fair, six-sided die is rolled. What is the probability of obtaining a 3 or an odd number? A. 1/6 B. 1/5 C. 1/4 D. 2/3 E. 1/2 15. At a certain business school, 400 students are members of the sailing club, the wine club, or both. If 200 students are members of the wine club and 50 students are members of both clubs, what is the probability that a student chosen at random is a member of the sailing club? A. 1/2 B. 5/8 C. 1/4 D. 3/8 E. 3/5 16. A bag contains six marbles: two red, two blue, and two green. If two marbles are drawn at random, what is the probability that they are the same color? A. 1/3 B. 1/2 C. 1/8 D. 1/4 E. 1/5 17. There are five students in a study group: two finance majors and three accounting majors. If two students are chosen at random, what is the probability that they are both accounting students? A. 3/10 B. 2/5 C. 1/5 D. 3/5 E. 4/5 18. Seven beads are in a bag: three blue, two red, and two green. If three beads are randomly drawn from the bag, what is the probability that they are not all blue? A. 5/7 B. 23/24 C. 6/7 D. 34/35 E. 8/13 19. A bag has six red marbles and six blue marbles. If two marbles are drawn randomly from the bag, what is the probability that they will both be red? A. 1/2 B. 11/12 C. 5/12 D. 5/22 E. 1/3:) Thanks V- Quote Link to comment Share on other sites More sharing options...
v-rap Posted April 1, 2008 Author Share Posted April 1, 2008 Also I found a refresher link from the past posts Reflections Vol20, No3, Aug 95 Quote Link to comment Share on other sites More sharing options...
Dynamo Posted April 1, 2008 Share Posted April 1, 2008 Thanks! will work out and ask you for answer :) Quote Link to comment Share on other sites More sharing options...
california Posted April 1, 2008 Share Posted April 1, 2008 1. B Probability of getting one blue bead = 3/9 = 1/3 Porbability of getting second blue bead = 2/8 = 1/4 Probability of getting blue bead in both picks = 1/3*1/4 = 1/12 2. C Probability of choosing s = 4/11 3. A Probability for first card to be not blue - 6/8 = 3/4 Probability for second card to be not blue - 5/7 Probablility for both cards to be not blue - 3/4*5/7 = 15/28 4. C Probability for heads - 1/2 Probability for 1 or 2 - 1/3 Probability for heads and 1 or 2 - 1/2*1/3 = 1/6 5. D Atleast on blue marble can be selected in three ways, BB, RB and BR Probability of getting BB - 7/10*6/9 = 7/15 Probability of getting RB - 3/10*7/9 = 7/30 Probability of getting BR - 7/10*3/9 = 7/30 Probability of getting atlease on blue - 7/15 + 7/30 + 7/30 = 14/15 6. B There are three odd numbers 1,3 and 5 Probability of getting odd number - 3/6 = 1/2 7. B Probability of choosing u - 2/8 = 1/4 8. E Probability that Sara draws a red marble - 2/6 = 1/3 Probability that victor draws a blue marble - 2/5 Probability that Sara draws a blue marble and Victor draws a red marble - 1/3 x 2/5 = 2/15 9. E There are 36 pairs of numbers when two dice are rolled. There four combinations that gives the sum of 5 - (1,4), (2,3), (3,2) and (4,1) Probability of the sum to be 5 - 4/36 = 1/9 10. D Probability of getting all four heads - 1/2 x 1/2 x 1/2 x 1/2 = 1/16 11. B Probability of the event not to occur = 1 - 5/9 = 4/9 12. D Probability of drawing green marble = 1 - (0.2 + 0.3 + 0.1) = 0.4 13. E Probability getting red marble = 3/9 = 1/3 Probability of getting 6 = 1/6 Probability of getting red marble and 6 = 1/3 x 1/6 = 1/18 14. E As 3 itself is an odd number, probability of getting odd number = 3/6 = 1/2 15. B Members in sailing club = 250 Probability of choosing member from sailing club = 250/400 = 5/8 16. E First marble can be any color. Probability of choosing second marble of the same color as the first one = 1/5 17. A Probability of first student to be accounting student - 3/5 Probability of second student to be accounting student - 2/4 = 1/2 Probability that both students to be accounting students - 3/5 x 1/2 = 3/10 18. D Probability of selecting all blue marbles in 3 picks - 3/7 x 2/6 x 1/5 = 1/35 Probability that all three of them are not blue = 1 - 1/35 = 34/35 19. D Probability that both are red marbles = 6/12 x 5/11 = 5/22 Quote Link to comment Share on other sites More sharing options...
Dynamo Posted April 1, 2008 Share Posted April 1, 2008 1. Probability of getting one blue bead = 3/9 = 1/3 i think 2/9 Quote Link to comment Share on other sites More sharing options...
Dynamo Posted April 1, 2008 Share Posted April 1, 2008 2. 4/11 Quote Link to comment Share on other sites More sharing options...
v-rap Posted April 1, 2008 Author Share Posted April 1, 2008 I have to admit I am no expert in probability. I am trying to learn. I am looking forward to see the solutions, However, there was a link way back on this forum, which had discussion on the same questions. I can find and post that. thanks V- :) Quote Link to comment Share on other sites More sharing options...
itsme_sanket Posted April 3, 2008 Share Posted April 3, 2008 hi california, I agree with all yours answers expext two #15 --> 150/400 = 3/8 #14 ---> i think eventhough 3 is odd number we need to consider different probablity for it. 1/2 + 1/6 ==> 4/12 ==> 1/3 Quote Link to comment Share on other sites More sharing options...
g.tatiana Posted April 3, 2008 Share Posted April 3, 2008 I didn't get how to crack the 5th question! I was choosing between 47/50 and 14/15 relying solely on logic, but I couldn't solve it. Can anybody write an explanation please????? And, after itsme sunket's post, I also doubt about q.№15! Quote Link to comment Share on other sites More sharing options...
g.tatiana Posted April 3, 2008 Share Posted April 3, 2008 And I agree with all the other answers! Quote Link to comment Share on other sites More sharing options...
vgp Posted April 3, 2008 Share Posted April 3, 2008 California is right! (200-50)+50+(x-50)=400 X=250 probability = 250/400=5/8 Quote Link to comment Share on other sites More sharing options...
vgp Posted April 3, 2008 Share Posted April 3, 2008 Just I tried to improvise a little about the question 14. There are 3 objects in the sack: red square, green ball and yellow pyramid. What is the probability to choose a red object or a square ? P=1/3 not 1/3+1/3=2/3 Quote Link to comment Share on other sites More sharing options...
vgp Posted April 3, 2008 Share Posted April 3, 2008 question 1: California is right again 9C2=36 3C2=3 3/36=1/12 Quote Link to comment Share on other sites More sharing options...
itsme_sanket Posted April 3, 2008 Share Posted April 3, 2008 @tantania hi i think ...5 question can be solved as probability of selecting 1 blue out of two selection is (3C1 * 7C1) / 10C2 probability of selecting 2 blue = (7C2) / 10C2 total probaility of selecting atleast one blue = (3C1 * 7C1) / 10C2 + (7C2) / 10C2 = 14/15 Quote Link to comment Share on other sites More sharing options...
bose Posted May 4, 2008 Share Posted May 4, 2008 i agree with all california's answers Quote Link to comment Share on other sites More sharing options...
abaya Posted September 5, 2011 Share Posted September 5, 2011 thanks for the questions. Quote Link to comment Share on other sites More sharing options...
Sumon1 Posted September 11, 2011 Share Posted September 11, 2011 Here is my answer without explanatio 1.B 2.C 3. 27/28 4.C 5.D 6.B 7.B 8.1/9 9.E 10.D 11.B 12.D 13.E 14.E 15.D 16.1/27 17.A 18.D 19.D Quote Link to comment Share on other sites More sharing options...
Sumon1 Posted September 11, 2011 Share Posted September 11, 2011 Here is my answer without explanation 1.B 2.C 3. 27/28 4.C 5.D 6.B 7.B 8.1/9 9.E 10.D 11.B 12.D 13.E 14.E 15.D 16.1/27 17.A 18.D 19.D Quote Link to comment Share on other sites More sharing options...
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