document.write( "Question 990553: how many 5 element subsets can be found in Set (1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20) \n" ); document.write( "

Algebra.Com's Answer #610668 by ikleyn(52803) $\"\"$ $\"About$

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\n" ); document.write( "S = {1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20}\r
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\n" ); document.write( "\n" ); document.write( "C(20,5) = $\"20%21%2F%28%2820+-+5%29%215%21%29\"$ = $\"20%21%2F%2815%215%21%29\"$ .\r
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\n" ); document.write( "\n" ); document.write( "Actually, you do not need to make long calculations. Notice that \r
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\n" ); document.write( "\n" ); document.write( " $\"20%21%2F15%21\"$ = 16*17*18*19*20.\r
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\n" ); document.write( "\n" ); document.write( "So, the answer is \r
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\n" ); document.write( "\n" ); document.write( " $\"20%21%2F%2815%215%21%29\"$ = $\"%2816%2A17%2A18%2A19%2A20%29%2F%282%2A3%2A4%2A5%29\"$ = 2*17*6*19*4 = \r
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\n" ); document.write( "\n" ); document.write( "= 15, 504 different 5 element subsets.\r
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