document.write( "Question 1192533: what is the smallest number of cells that need to be coloured in a 5 by 5 square so that any 1 by 4 or 4 by 1 rectangle lying inside the square has at least one cell coloured. \n" ); document.write( "

Algebra.Com's Answer #824432 by ikleyn(52805) $\"\"$ $\"About$

You can put this solution on YOUR website!
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\n" ); document.write( "\n" ); document.write( "I managed to solve the problem with the lesser number of colored squares, 6.\r
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document.write( "   +---+---+---+---+---+ \r\n" );
document.write( "   |   |   | X |   |   | \r\n" );
document.write( "   +---+---+---+---+---+ \r\n" );
document.write( "   |   | X |   |   |   | \r\n" );
document.write( "   +---+---+---+---+---+ \r\n" );
document.write( "   | X |   |   |   | X | \r\n" );
document.write( "   +---+---+---+---+---+  \r\n" );
document.write( "   |   |   |   | X |   | \r\n" );
document.write( "   +---+---+---+---+---+ \r\n" );
document.write( "   |   |   | X |   |   | \r\n" );
document.write( "   +---+---+---+---+---+ \r\n" );
document.write( "

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\n" ); document.write( "\n" ); document.write( "ANSWER. 6.\r
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