SOLUTION: Andrew has seven 20 cent coins and five 50 cent coins in his piggy bank. What is the smallest number of coins he might have to shake out of his piggy bank to be certain of having

Question 765640: Andrew has seven 20 cent coins and five 50 cent coins in his piggy bank. What is the smallest number of coins he might have to shake out of his piggy bank to be certain of having two 50 cent coins?
I have tried to experiment with my own doggy bank and the 50 and 20 cent coins and got a different answer each time. This makes me think that the answer is 10 coins to be certain.
Answer by stanbon(75887) (Show Source): You can put this solution on YOUR website!
Andrew has seven 20 cent coins and five 50 cent coins in his piggy bank. What is the smallest number of coins he might have to shake out of his piggy bank to be certain of having two 50 cent coins?
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The first 7 coins might be 20 cent pieces.
The next 2 must be 50 cent pieces.
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Answer:: 9
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Ches,
Stan H.
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