document.write( "Question 1064626: C(10,r) =120. What is r?\r
\n" ); document.write( "\n" ); document.write( "Please explain how you get r. Thanks \n" ); document.write( "

Algebra.Com's Answer #679712 by math_helper(2461) $\"\"$ $\"About$

You can put this solution on YOUR website!
Since the numbers are small, I'd use trial-and-error:\r
\n" ); document.write( "\n" ); document.write( "C(10,5) = $\"+10%21%2F%285%21%2A5%21%29+\"$ = $\"+10%2A9%2A8%2A7%2A6+%2F+%285%2A4%2A3%2A2%29+=+252+\"$
\n" ); document.write( "C(10,6) = $\"+10%21%2F%286%21%2A4%21%29+\"$ = $\"+10%2A9%2A8%2A7+%2F+%284%2A3%2A2%29+=+210+\"$
\n" ); document.write( "C(10,7) = $\"+10%21%2F%287%21%2A3%21%29+\"$ = $\"++10%2A9%2A8+%2F+%283%2A2%29+=+120+\"$ \r
\n" ); document.write( "\n" ); document.write( "So C(10,7) satisfies the equation, so r=7 works… but note that C(10,7) = C(10,10-7) = C(10,3) so r=3 is also a solution.\r
\n" ); document.write( "\n" ); document.write( "Solutions are $\"+highlight%28r=3%29+\"$ and $\"+highlight%28r=7%29+\"$
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