document.write( "Question 982206: Arithmetic Sequence Problem:
\n" ); document.write( "A mosaic in the shape of an equilateral triangle is 25 ft on each side. Each tile in the mosaic is in the shape of an equilateral triangle, 12 inches to a side. The tiles are alternate in colour like △▾△ (sorry I cant show the picture) . How many tiles of each colour will be needed?
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Algebra.Com's Answer #603094 by KMST(5328)\"\" \"About 
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Each tile in the mosaic is in the shape of an equilateral triangle,
\n" ); document.write( "\"12inches=1foot\" to a side.\r
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\n" ); document.write( "\n" ); document.write( "On the base of that triangular mosaic,
\n" ); document.write( "you have the bases of \"25\" tiles of color \"X\" .
\n" ); document.write( "Tiles of color \"A\" will be at all 3 vertices of the triangular mosaic,
\n" ); document.write( "and all 3 sides of the triangular mosaic would look just the same,
\n" ); document.write( "so it does not matter which one I choose to call the base of the triangular mosaic.\r
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\n" ); document.write( "\n" ); document.write( "In between the \"25\" base-down, vertex-up triangles of color \"X\" ,
\n" ); document.write( "there will be \"25-1=24\" base-up, vertex-down triangles of color \"Y\" ,
\n" ); document.write( "completing the first row/layer of tiles at the base of the triangular mosaic.\r
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\n" ); document.write( "\n" ); document.write( "Atop each of those \"24\" base-up, vertex-down triangles of color \"Y\" ,
\n" ); document.write( "there will be one base-down, vertex-up triangle of color \"X\" ,
\n" ); document.write( "for a total of \"24\" base-down, vertex-up triangles of color \"X\"
\n" ); document.write( "on the second row of the triangular mosaic.\r
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\n" ); document.write( "\n" ); document.write( "In between the \"24\" base-down, vertex-up triangles of color \"X\" on the second row,
\n" ); document.write( "there will be \"24-1=23\" base-up, vertex-down triangles of color \"Y\" ,
\n" ); document.write( "completing the second row/layer of tiles at the base of the triangular mosaic.\r
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\n" ); document.write( "\n" ); document.write( "That patter repeats, so you have
\n" ); document.write( "\"N%5BX%5D=25%2B24%2B23%2B%22...%22%2B3%2B2%2B1\" tiles of color \"X\" , and
\n" ); document.write( "\"N%5BY%5D=24%2B23%2B22%2B%22...%22%2B3%2B2%2B1%7D%7D+tiles+of+color+%7B%7B%7BY\" .
\n" ); document.write( "Those numbers are the sums of the \"25\" and \"24\" first terms of the arithmetic sequence with first term \"1\" and common difference \"1\" .
\n" ); document.write( "The easiest way to calculate the sum \"a%5B1%5D%2Ba%5B2%5D%2Ba%5B3%5D%2B%22...%22%2Ba%5Bn-2%5D%2Ba%5Bn-1%5D%2Ba%5Bn%5D\" when you know
\n" ); document.write( "the number \"n\" of terms you are adding,
\n" ); document.write( "the first term \"a%5B1%5D\" you are adding, and
\n" ); document.write( "the last term \"a%5Bn%5D\" you are adding is
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\n" ); document.write( "So,
\n" ); document.write( "\"N%5BY%5D=24%2A%2824%2B1%29%2F2=12%2A25=highlight%28300%29\"
\n" ); document.write( "and
\n" ); document.write( "\"N%5Bx%5D=N%5BY%5D%2B25=300%2B25=highlight%28325%29\"
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