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Balls of same color

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by punitkaur » Mon Nov 02, 2009 9:05 am
30. In a jar there are 21 white balls, 24 green balls and 32 blue balls. How many balls must be taken out in order to make sure we have 23 balls of the same color?

a) 23
b) 46
c) 57
d) 66
e) 67

My answer is 54 and i cant find it in the choices. Also I cant understand the explanation given in the source.
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by jzdchou » Mon Nov 02, 2009 10:28 am
I got 66. I am not sure if it is right.

W=21
G=24
B=32

Assuming you have the worst of luck and keep getting 1W, 1G, 1B, 1W, 1G, 1B etc etc

now after 63 tries (21X3). No more W, but 3 G and 11 B left. Ane you have 21W, 21G, 21B taken out.

If you get 2G or 2B in a row, then you get 23 of one color (B or G), which then ans = 63 + 2 = 65
BUT
You can get 1G, and then 1B, and then either 1G or 1B on the third try, so the ans = 63 + 3 = 66

D
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Re: Balls of same color

by sanjana » Tue Nov 03, 2009 3:29 am
punitkaur wrote:30. In a jar there are 21 white balls, 24 green balls and 32 blue balls. How many balls must be taken out in order to make sure we have 23 balls of the same color?

a) 23
b) 46
c) 57
d) 66
e) 67

My answer is 54 and i cant find it in the choices. Also I cant understand the explanation given in the source.
Whats the answer given in the source?
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by life is a test » Tue Nov 03, 2009 7:33 am
since you need 23 of the same color it cant be white balls. assume worst case scenario:
21 white balls + 22 green balls + 22 blue balls = 65.

the 66th ball has to be either green or and in either case it will be the 23rd ball of that color so you will be guaranteed to get 23 balls of same color.

OA pls?
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by tarun.kirla » Thu Nov 05, 2009 12:46 pm
21 white balls + 23 blue balls +23 green balls = 67
21 white balls + 23 green balls +23 blue balls = 67
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