document.write( "Question 1104515: The sum of 1 + r + r^2 + r^3 + .... = 1.85. What is the value of the sum r + r^3 + r^5 + r^7....? \n" ); document.write( "

Algebra.Com's Answer #719237 by greenestamps(13200) $\"\"$ $\"About$

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\n" ); document.write( "The sum of an infinite geometric series with first term a and common ratio r (|r|<1) is

\n" ); document.write( " $\"S+=+a%2F%281-r%29\"$

\n" ); document.write( "We are told that
\n" ); document.write( " $\"1%2F%281-r%29+=+1.85\"$
\n" ); document.write( " $\"1.85-1.85r+=+1\"$
\n" ); document.write( " $\"1.85r+=+.85\"$
\n" ); document.write( " $\"r+=+.85%2F1.85+=+17%2F37\"$

\n" ); document.write( "The series whose sum we are to find has first term r and common ratio r^2; the sum of that infinite series is
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