document.write( "Question 1067722: When 15 is appended to a list of integers, the mean is increased by 2. When 1 is appended to the enlarged list, the mean of the enlarged list is decreased by 1. How many integers were in the original list? \n" ); document.write( "
Algebra.Com's Answer #682832 by josmiceli(19441)\"\" \"About 
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Let \"+n+\" = the number of integers in the original list
\n" ); document.write( "Let \"+m+\" = the mean of the original list
\n" ); document.write( "------------------------
\n" ); document.write( "Originally, the total, \"+T+\", of the integers was:
\n" ); document.write( "\"+m+=+T%2Fn+\"
\n" ); document.write( "\"+T+=+m%2An+\"
\n" ); document.write( "--------------------
\n" ); document.write( "Add \"+15+\" to the list
\n" ); document.write( "(1) \"+m+%2B+2+=+%28+m%2An+%2B+15+%29+%2F+%28+n+%2B+1+%29+\"
\n" ); document.write( "--------------------------------------
\n" ); document.write( "Add \"++1+\" to the enlarged list
\n" ); document.write( "(2) \"+m+%2B+2+-+1+=+%28+m%2An+%2B+15+%2B+1+%29+%2F+%28+n+%2B+2+%29+\"
\n" ); document.write( "--------------------------------------
\n" ); document.write( "(1) \"+%28+m+%2B+2+%29%2A%28+n+%2B+1+%29+=+m%2An+%2B+15+\"
\n" ); document.write( "(1) \"+m%2An+%2B+2n+%2B+m+%2B+2+=+m%2An+%2B+15+\"
\n" ); document.write( "(1) \"+m+%2B+2n+=+13+\"
\n" ); document.write( "and
\n" ); document.write( "(2) \"+%28+m+%2B+1+%29%2A%28+n+%2B+2+%29+=+m%2An+%2B+16+\"
\n" ); document.write( "(2) \"+m%2An+%2B+n+%2B+2m+%2B+2+=+m%2An+%2B+16+\"
\n" ); document.write( "(2) \"+2m+%2B+n+=+14+\"
\n" ); document.write( "-----------------------
\n" ); document.write( "Multiply both sides of (2) by \"+2+\"
\n" ); document.write( "and subtract (1) from (2)
\n" ); document.write( "(2) \"+4m+%2B+2n+=+28+\"
\n" ); document.write( "(1) \"+-m+-+2m+=+-13+\"
\n" ); document.write( "------------------------
\n" ); document.write( "\"+3m+=+15+\"
\n" ); document.write( "\"+m+=+5+\"
\n" ); document.write( "and
\n" ); document.write( "(1) \"+m+%2B+2n+=+13+\"
\n" ); document.write( "(1) \"+5+%2B+2n+=+13+\"
\n" ); document.write( "(1) \"+2n+=+8+\"
\n" ); document.write( "(1) \"+n+=+4+\"
\n" ); document.write( "-----------------------------------------
\n" ); document.write( "There were 4 integers in the original list
\n" ); document.write( "-----------------------------------------
\n" ); document.write( "check:
\n" ); document.write( "(1) \"+T+=+m%2An+\"
\n" ); document.write( "(1) \"+T+=+5%2A4+\"
\n" ); document.write( "(1) \"+T+=+20+\"
\n" ); document.write( "--------------------
\n" ); document.write( "(1) \"+m+%2B+2+=+%28+m%2An+%2B+15+%29+%2F+%28+n+%2B+1+%29+\"
\n" ); document.write( "(1) \"+5+%2B+2+=+%28+20+%2B+15+%29+%2F+%28+4+%2B+1+%29+\"
\n" ); document.write( "(1) \"+7+=+35%2F5+\"
\n" ); document.write( "(1) \"+7+=+7+\"
\n" ); document.write( "and
\n" ); document.write( "(2) \"+m+%2B+2+-+1+=+%28+m%2An+%2B+15+%2B+1+%29+%2F+%28+n+%2B+2+%29+\"
\n" ); document.write( "(2) \"+5+%2B+2+-+1+=+%28+20+%2B+15+%2B+1+%29+%2F+%28+4+%2B+2+%29+\"
\n" ); document.write( "(2) \"+6+=+36%2F6+\"
\n" ); document.write( "(2) \"+6+=+6+\"
\n" ); document.write( "OK\r
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