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प्रश्न
If nPr = 720(nCr), then r is equal to:
विकल्प
4
5
6
7
उत्तर
6
Explanation:
Given nPr = 720(nCr)
`(n!)/((n-r)!) = 720 (n!)/(r!(n-r)!)`
1 = `720/(r!)`
r! = 720
r! = 6 × 5 × 4 × 3 × 2 × 1
r! = 6!
r = 6
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