document.write( "Question 208973: Find the ratio a:c if a:b= 1:2, b:d = 4:5, d:c = 3:1 \n" ); document.write( "
Algebra.Com's Answer #157994 by Theo(13342)\"\" \"About 
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Find the ratio a:c if a:b= 1:2, b:d = 4:5, d:c = 3:1
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\n" ); document.write( "x : y is the same as \"x+%2F+y\" is the same as x divided by y
\n" ); document.write( "see reference: http://www.icoachmath.com/sitemap/Ratio.html
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\n" ); document.write( "a:b means \"a%2Fb+=+1%2F2\" which means that \"a+=+b%2F2\" and \"b+=+2%2Aa\"
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\n" ); document.write( "b:d means \"b%2Fd+=+4%2F5\" which means that \"b+=+4d%2F5\" and \"d+=+5b%2F4\"
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\n" ); document.write( "d:c means \"d%2Fc+=+3%2F1\" which means that \"d+=+3c\" and \"c+=+d%2F3\"
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\n" ); document.write( "now that you have these translations out of the way you can solve.
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\n" ); document.write( "a:c means \"a%2Fc\"
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\n" ); document.write( "to find \"a%2Fc\" you need to find relationships in terms of a and c and then solve.
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\n" ); document.write( "in order to get a relationship from a to c, you need to go through b and d because there is no direct relationship between a and c.
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\n" ); document.write( "start with the relationship between a and b.
\n" ); document.write( "\"a+=+b%2F2\"
\n" ); document.write( "get the relationship from b to d
\n" ); document.write( "\"b+=+4d%2F5\"
\n" ); document.write( "replace b with \"4d%2F5\" to get:
\n" ); document.write( "\"+a+=+%284d%2F5%29%2F2\" which becomes:
\n" ); document.write( "\"a+=+4d%2F10\"
\n" ); document.write( "get the relationship from d to c
\n" ); document.write( "\"d+=+3c\"
\n" ); document.write( "replace d with 3c to get:
\n" ); document.write( "\"a+=+%284%2A3c%29%2F10\" which becomes:
\n" ); document.write( "\"a+=+12c%2F10\" which becomes:
\n" ); document.write( "\"a+=+6c%2F5\"
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\n" ); document.write( "\"a+=+6c%2F5\" is the same as:
\n" ); document.write( "\"a%2Fc+=+6%2F5\" which is the same as:
\n" ); document.write( "\"a%3Ac+=+6%3A5\"
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\n" ); document.write( "to confirm, let's try to find c directly and then try to find c indirectly.
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\n" ); document.write( "let a = 6
\n" ); document.write( "if \"a+=+6c+%2F+5\", then c must equal to \"5a%2F6\" = \"%285%2A6%29%2F6\" = \"5\"
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\n" ); document.write( "we know that a = 6 and c = 5 solving directly.
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\n" ); document.write( "let's find c indirectly.
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\n" ); document.write( "we start off with a = 6
\n" ); document.write( "we know that \"b\" = \"2%2Aa\" = \"2%2A6\" = \"12\"
\n" ); document.write( "we know that \"d\" = \"%285%2Ab%29%2F4\" = \"%285%2A12%29%2F4\" = \"15\"
\n" ); document.write( "we know that \"c\" = \"d%2F3\" = \"15%2F3\" = \"5\"
\n" ); document.write( "we have \"a+=+6\" and \"c+=+5\" solving indirectly.
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\n" ); document.write( "the formulas check out and the relationship you are looking for is:
\n" ); document.write( "\"a%3Ac+=+6%3A5\"
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\n" ); document.write( "is there an easier way to do this?
\n" ); document.write( "yes there is
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\n" ); document.write( "the shortcut method is as follows:
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\n" ); document.write( "you have \"a%3Ac\" = \"%28a%3Ab%29+%2A+%28b%3Ad%29+%2A+%28d%3Ac%29\"
\n" ); document.write( "you know those ratios are:
\n" ); document.write( "\"1%3A2\" and \"4%3A5\" and \"3%3A1\"
\n" ); document.write( "you know this is the same as:
\n" ); document.write( "\"1%2F2\" and \"4%2F5\" and \"3%2F1\"
\n" ); document.write( "so you have:
\n" ); document.write( "\"a%2Fc\" = \"%28a%2Fb%29+%2A+%28b%2Fd%29+%2A+%28d%2Fc%29\" = \"%281%2F2%29+%2A+%284%2F5%29+%2A+%283%2F1%29\" = \"%281%2A4%2A3%29%2F%282%2A5%2A1%29\" = \"12%2F10\" = \"6%2F5\"
\n" ); document.write( "your ratio for \"a%2Fc+=+6%2F5\"
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