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Dhaka Junior 2011/2

Posted: Wed Feb 02, 2011 8:21 am
by Moon
2. In a box there are $420$ balls of $20$ different colors. What is the minimum number of balls one need to pick so that he can be sure of having at least two balls of same colors?

Re: Dhaka Junior 2011/2

Posted: Wed Feb 02, 2011 11:30 am
by Mehfuj Zahir
At least 21 balls needed

Re: Dhaka Junior 2011/2

Posted: Wed Nov 30, 2011 6:49 pm
by ataher.sams
Yes.. 21 balls..