Dhaka Junior 2011/2

Problem for Junior Group from Divisional Mathematical Olympiad will be solved here.
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Moon
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Dhaka Junior 2011/2

Unread post by Moon » Wed Feb 02, 2011 8:21 am

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?
"Inspiration is needed in geometry, just as much as in poetry." -- Aleksandr Pushkin

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Mehfuj Zahir
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Re: Dhaka Junior 2011/2

Unread post by Mehfuj Zahir » Wed Feb 02, 2011 11:30 am

At least 21 balls needed

ataher.sams
Posts: 20
Joined: Wed Nov 30, 2011 6:24 pm
Location: Madarbari, Chittagong ,Bangladesh.

Re: Dhaka Junior 2011/2

Unread post by ataher.sams » Wed Nov 30, 2011 6:49 pm

Yes.. 21 balls..

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