In a jar there are 15 white balls, 25 red balls, 10 blue balls and 20 green balls.
How many balls must be taken out in order to make sure we took out 8 of the same color?
a) 8
b) 23
c) 29
d) 32
e) 53
nice one...
15 white balls, 25 red balls, 10 blue balls and 20 green
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correct!
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- sumanr84
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From where these questions are popping out ??arora007 wrote:In a jar there are 15 white balls, 25 red balls, 10 blue balls and 20 green balls.
How many balls must be taken out in order to make sure we took out 8 of the same color?
a) 8
b) 23
c) 29
d) 32
e) 53
nice one...
I am on a break !!
- arora007
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https://www.urch.com/forums/gre-math/867 ... ems-2.html
https://www.scribd.com/doc/25455404/Probability
https://www.scribd.com/doc/25455404/Probability
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- sumanr84
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arora bhai..I am following your maths thread these days..these Qs are good one as you don't need much math to solve, but rather logical inference, CR kinda..
I am on a break !!
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excuse me, can you please explain why there is a number 7 here?nithi_mystics wrote:29 balls
7+7+7+8 = 29
- Gurpinder
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Read this!diebeatsthegmat wrote:excuse me, can you please explain why there is a number 7 here?nithi_mystics wrote:29 balls
7+7+7+8 = 29
https://www.beatthegmat.com/bloody-jail- ... 19469.html
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In order to guarantee that we get 8 of the same color, we need to consider the worst-case scenario. In the problem above, the worst-case scenario would be to choose 7 of each color:diebeatsthegmat wrote:excuse me, can you please explain why there is a number 7 here?nithi_mystics wrote:29 balls
7+7+7+8 = 29
7+7+7+7 = 28.
Thus, choosing only 28 balls isn't sufficient, because we could get only 7 of each color. To guarantee that we get 8 of one of the colors, we need to choose one more ball: 28+1 = 29.
The correct answer is C.
Does this help?
Last edited by GMATGuruNY on Thu Dec 27, 2012 7:30 pm, edited 1 time in total.
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If you picked 28 balls is it not possible that you picked 25 red and 3 green? Therefore not meeting the criteria of pulling out 8 of the same color?
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If you picked 28 balls, you could get 8 of the same color, but getting 8 of the same color wouldn't be guaranteed because you also could choose only 7 of each color. To guarantee that you get 8 of the same color, 1 more ball has to be chosen.HPengineer wrote:If you picked 28 balls is it not possible that you picked 25 red and 3 green? Therefore not meeting the criteria of pulling out 8 of the same color?
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worst case scenario, GMAT's favorite trickarora007 wrote:In a jar there are 15 white balls, 25 red balls, 10 blue balls and 20 green balls.
How many balls must be taken out in order to make sure we took out 8 of the same color?
a) 8
b) 23
c) 29
d) 32
e) 53
nice one...
Until 28 balls, as there are 4 different colors, we can at worst expect 7 of each color; just 1 more ball and we definitely have 8 of same color in hand.
[spoiler]C[/spoiler]
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damn correct..!GMATGuruNY wrote:If you picked 28 balls, you could get 8 of the same color, but getting 8 of the same color wouldn't be guaranteed because you also could choose only 7 of each color. To guarantee that you get 8 of the same color, 1 more ball has to be chosen.HPengineer wrote:If you picked 28 balls is it not possible that you picked 25 red and 3 green? Therefore not meeting the criteria of pulling out 8 of the same color?
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The worst case scenario would be having to draw 7 balls of each color so that we wouldn't have 8 balls of any one color. However, if we were to remove just one more ball, regardless of the color, we would then have 8 balls of one color. Thus, we need to remove 7 x 4 + 1 = 29 balls.arora007 wrote:In a jar there are 15 white balls, 25 red balls, 10 blue balls and 20 green balls.
How many balls must be taken out in order to make sure we took out 8 of the same color?
a) 8
b) 23
c) 29
d) 32
e) 53
Answer: C
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