Fiver Posted August 28, 2008 Share Posted August 28, 2008 A student is asked to pick marbles from a bag that contains 18 marbles. Eight marbles are red, 4 are green, and 6 are black. What is the minimum number of marbles that a blindfolded student would have to draw from the bag to be certain of having at least three marbles of the same color? A) 5 B) 6 C) 7 D) 13 E) 14 Please post ur reasoning. Quote Link to comment Share on other sites More sharing options...
venkat007 Posted August 28, 2008 Share Posted August 28, 2008 Ans : 7 There are 3 different colours. To be certain that the student has selected atleast 3 marbles of same colour. Assume that he has pciked up 1 from each box. R G B 1 1 1 1 1 1 After picking up first 6 balls in that way. Now he will have 2 from each colour. The 7th ball of any colour will satisfy the condition of atleast 3 marbles of same colour. Quote Link to comment Share on other sites More sharing options...
Queen09 Posted August 28, 2008 Share Posted August 28, 2008 C Consider the worst case. Say the person started picking ang got 2 Red, 2 Green and 2 Blues. The 7th pick will 100% result in the condition "three marbles of the same color" Is this correct ? Quote Link to comment Share on other sites More sharing options...
CrazyGmatter Posted August 28, 2008 Share Posted August 28, 2008 IMO C.. agree with Queen09 and venkat Quote Link to comment Share on other sites More sharing options...
Fiver Posted August 29, 2008 Author Share Posted August 29, 2008 C is the OA. What i thought that it meant 3 of the same colour at one pick! Then it becomes 14, which also happens to be an option (wrong one though). Quote Link to comment Share on other sites More sharing options...
Rathna Posted August 29, 2008 Share Posted August 29, 2008 Agree with Venkat's Reasoning, 7 Quote Link to comment Share on other sites More sharing options...
bose Posted September 20, 2008 Share Posted September 20, 2008 1 red, 2 green, 2 blue, 2 red 7 ans Quote Link to comment Share on other sites More sharing options...
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