## ordered pair (n,r)

For students of class 11-12 (age 16+)
jagdish
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Joined: Wed Jan 19, 2011 2:21 pm

### ordered pair (n,r)

Total number of whole number integer ordered pair $(n,r)$ in $\displaystyle \binom{n}{r} = 120$
jagdish

asif e elahi
Posts: 183
Joined: Mon Aug 05, 2013 12:36 pm
jagdish wrote:Total number of whole number integer ordered pair $(n,r)$ in $\displaystyle \binom{n}{r} = 120$
You can use the well known fact that $\frac{n}{gcd(n,k)} \mid \binom{n}{k} \text{ } \forall n,k\in \mathbb{N}$ with $k\leq n$.