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| | == Problem == | | == Problem == |
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| − | How many of the twelve pentominoes pictured below have at least one line of symettry? | + | How many of the twelve pentominoes at least one line of symmetry? |
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| − | <math> \textbf{(A)}\ 3 \qquad \textbf{(B)}\ 4 \qquad \textbf{(C)}\ 5 \qquad \textbf{(D)}\ 6 \qquad \textbf{(E)}\ 7 | + | <math> \textbf{(A)}\ 3 \qquad \textbf{(B)}\ 4 \qquad \textbf{(C)}\ 5 \qquad \textbf{(D)}\ 6 \qquad \textbf{(E)}\ 7 </math> |
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| − | [asy]
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| − | unitsize(5mm);
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| − | defaultpen(linewidth(1pt));
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| − | draw(shift(2,0)*unitsquare);
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| − | draw(shift(2,1)*unitsquare);
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| − | draw(shift(2,2)*unitsquare);
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| − | draw(shift(1,2)*unitsquare);
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| − | draw(shift(0,2)*unitsquare);
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| − | draw(shift(2,4)*unitsquare);
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| − | draw(shift(2,5)*unitsquare);
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| − | draw(shift(2,6)*unitsquare);
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| − | draw(shift(1,5)*unitsquare);
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| − | draw(shift(0,5)*unitsquare);
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| − | draw(shift(4,8)*unitsquare);
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| − | draw(shift(3,8)*unitsquare);
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| − | draw(shift(2,8)*unitsquare);
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| − | draw(shift(1,8)*unitsquare);
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| − | draw(shift(0,8)*unitsquare);
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| − | draw(shift(6,8)*unitsquare);
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| − | draw(shift(7,8)*unitsquare);
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| − | draw(shift(8,8)*unitsquare);
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| − | draw(shift(9,8)*unitsquare);
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| − | draw(shift(9,9)*unitsquare);
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| − | draw(shift(6,5)*unitsquare);
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| − | draw(shift(7,5)*unitsquare);
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| − | draw(shift(8,5)*unitsquare);
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| − | draw(shift(7,6)*unitsquare);
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| − | draw(shift(7,4)*unitsquare);
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| − | draw(shift(6,1)*unitsquare);
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| − | draw(shift(7,1)*unitsquare);
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| − | draw(shift(8,1)*unitsquare);
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| − | draw(shift(6,0)*unitsquare);
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| − | draw(shift(7,2)*unitsquare);
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| − | draw(shift(11,8)*unitsquare);
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| − | draw(shift(12,8)*unitsquare);
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| − | draw(shift(13,8)*unitsquare);
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| − | draw(shift(14,8)*unitsquare);
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| − | draw(shift(13,9)*unitsquare);
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| − | draw(shift(11,5)*unitsquare);
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| − | draw(shift(12,5)*unitsquare);
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| − | draw(shift(13,5)*unitsquare);
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| − | draw(shift(11,6)*unitsquare);
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| − | draw(shift(13,4)*unitsquare);
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| − | draw(shift(11,1)*unitsquare);
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| − | draw(shift(12,1)*unitsquare);
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| − | draw(shift(13,1)*unitsquare);
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| − | draw(shift(13,2)*unitsquare);
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| − | draw(shift(14,2)*unitsquare);
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| − | draw(shift(16,8)*unitsquare);
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| − | draw(shift(17,8)*unitsquare);
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| − | draw(shift(18,8)*unitsquare);
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| − | draw(shift(17,9)*unitsquare);
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| − | draw(shift(18,9)*unitsquare);
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| − | draw(shift(16,5)*unitsquare);
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| − | draw(shift(17,6)*unitsquare);
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| − | draw(shift(18,5)*unitsquare);
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| − | draw(shift(16,6)*unitsquare);
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| − | draw(shift(18,6)*unitsquare);
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| − | draw(shift(16,0)*unitsquare);
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| − | draw(shift(17,0)*unitsquare);
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| − | draw(shift(17,1)*unitsquare);
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| − | draw(shift(18,1)*unitsquare);
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| − | draw(shift(18,2)*unitsquare);[/asy] </math>
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| | == Solution == | | == Solution == |
