document.write( "Question 1084552: The sum to m term of the series 1 +11+111...... upto m term is equal to: \n" ); document.write( "
Algebra.Com's Answer #698706 by math_helper(2461)\"\" \"About 
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\"+a%5Bk%5D+=+%281%2F9%29%2810%5Ek+-+1%29+\" k=1,2,3,…\r
\n" ); document.write( "\n" ); document.write( "\"+S%5Bn%5D+=+sum+%28++%281%2F9%29%2A%2810%5Ek+-+1%29%2C+k=1%2C+n+%29+\"\r
\n" ); document.write( "\n" ); document.write( "\"+S%5B1%5D++=+1++\"
\n" ); document.write( "\"+S%5B2%5D+=+12+\"
\n" ); document.write( "\"+S%5B3%5D+=+123+\"
\n" ); document.write( "--
\n" ); document.write( "\"+9%2AS%5B1%5D++=+9++\"
\n" ); document.write( "\"+9%2AS%5B2%5D+=+108+\"
\n" ); document.write( "\"+9%2AS%5B3%5D+=+1107++\"\r
\n" ); document.write( "\n" ); document.write( "Didn't see how 9*S[n] would help, ideally looking for something that is closer to 10^n for each S[n], so we can find a pattern in the amounts to subtract from 10^n to arrive at S[n]:\r
\n" ); document.write( "\n" ); document.write( "—
\n" ); document.write( "Note that
\n" ); document.write( "\"+81%2AS%5B1%5D+=+81+=+10%5E2+-+10+-+9++\"
\n" ); document.write( "\"+81%2AS%5B2%5D+=+972+=+10%5E3+-+10+-+9%2A2+\"
\n" ); document.write( "\"+81%2AS%5B3%5D+=+9963+=+10%5E4+-+10+-+9%2A3+\"\r
\n" ); document.write( "\n" ); document.write( "gives us \"+81%2AS%5Bn%5D+=+10%5E%28n%2B1%29+-10+-+9n+\"
\n" ); document.write( "and \"+highlight%28S%5Bn%5D+=+%281%2F81%29%2810%5E%28n%2B1%29+-+10+-+9n%29%29+\"\r
\n" ); document.write( "\n" ); document.write( "—\r
\n" ); document.write( "\n" ); document.write( "Spot Check:
\n" ); document.write( " (ok)
\n" ); document.write( " (ok)
\n" ); document.write( "—\r
\n" ); document.write( "\n" ); document.write( "I found this by trial and error, maybe another tutor has a more structured approach.
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