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nCr Definitions and Properties

If n P r =7...

Question

If $^{n} P_{r} = 720$ and $^{n} C_{r} = 120$ , then what is the value of 'r'.

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Solution

$^{n} P_{r} = 720$ & $^{n} C_{r} = 120$
As $^{n} P_{r} = r!^{n} C_{r} \Rightarrow r! = 6$
$r = 3$

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Similar questions

{^{n} P}_{r} = 720

{^{n} C}_{r} = 120

r

If $^{n} P_{r} = 720$ and $^{n} C_{r} = 120$ , find the value of r.

Q. Find the value of

n

r

^{n} P_{r} = 720

^{n} C_{r} = 120

{^{n} P}_{r} = {^{n} P}_{r + 1}

{^{n} C}_{r} = {^{n} C}_{r - 1}

(n, r)

^{n} P_{r} = 30240

^{n} C_{r} = 252

, then the ordered pair

(n, r)

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