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If nPr = 720(nCr), then r is equal to: (a) 4 (b) 5 (c) 6 (d) 7 |
Answer» (c) 6 Given nPr = 720(nCr) \(\frac{n!}{(n-r)!}\) = 720 \(\frac{n!}{r!(n-r)!}\) 1 = \(\frac{720}{r!}\) r! = 720 r! = 6 x 5 x 4 x 3 x 2 x 1 r! = 6! r = 6 |
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