In a jar there are 15 white balls, 25 red balls, 10 blue balls and 20 : GMAT Problem Solving (PS)
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# In a jar there are 15 white balls, 25 red balls, 10 blue balls and 20

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Manager
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In a jar there are 15 white balls, 25 red balls, 10 blue balls and 20 [#permalink]

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02 Nov 2009, 10:59
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Question Stats:

61% (01:49) correct 39% (01:14) wrong based on 105 sessions

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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
[Reveal] Spoiler: OA

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Re: In a jar there are 15 white balls, 25 red balls, 10 blue balls and 20 [#permalink]

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02 Nov 2009, 11:23
The question asks about how many balls MUST be taken out in order to make sure we took out 8 of the same color.

Now, in this case we have to be sure about our answer when we can say we have taken out 8 balls of same color.

Favorable case will be if we take out first eight balls and all of them are of the same color. But that is a favorable case and may not always be true.

A worst case will be when you are 100% sure that you have achieved the desired result.

As in this case: if you draw out first 28 balls and they are 7 of each color, W, R, B, G.
Now you know that any ball you take out next will be of any one of the above colors and hence you'll have 8 ball of same color.

So ans is 29.

I hope it's clear.
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Re: In a jar there are 15 white balls, 25 red balls, 10 blue balls and 20 [#permalink]

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02 Nov 2009, 22:35
kylexy 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

Thats 29 in C.

I love these types of questions..
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Re: In a jar there are 15 white balls, 25 red balls, 10 blue balls and 20 [#permalink]

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03 Nov 2009, 15:44
I don't get why there will be 7 of each when we draw out 28 balls. Could you please elaborate?
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Re: In a jar there are 15 white balls, 25 red balls, 10 blue balls and 20 [#permalink]

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04 Nov 2009, 05:08
Arora2m this one is for you :

Black Blue Yellow Green
1 1 1 1
1 1 1 1
.
.
.
.
.

similar pattern 7 times. the next ball will have to be from either of the colors and making the total tally of that color to 8 balls
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Re: In a jar there are 15 white balls, 25 red balls, 10 blue balls and 20 [#permalink]

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05 Nov 2009, 08:39
HI where do we come across these type of questions in og 11.If you could point out the question numbers it will be really greatful asap.
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Re: In a jar there are 15 white balls, 25 red balls, 10 blue balls and 20 [#permalink]

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12 May 2011, 03:12
nice question.

take 7 out of each color.7*4 + 1 = 29
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Re: In a jar there are 15 white balls, 25 red balls, 10 blue balls and 20 [#permalink]

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12 May 2016, 09:59
Hello from the GMAT Club BumpBot!

Thanks to another GMAT Club member, I have just discovered this valuable topic, yet it had no discussion for over a year. I am now bumping it up - doing my job. I think you may find it valuable (esp those replies with Kudos).

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Re: In a jar there are 15 white balls, 25 red balls, 10 blue balls and 20 [#permalink]

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12 May 2016, 14:02
kylexy 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

Check other Worst Case Scenario Questions from our Special Questions Directory to understand the concept better.
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Re: In a jar there are 15 white balls, 25 red balls, 10 blue balls and 20   [#permalink] 12 May 2016, 14:02
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