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Category: Permutation and Combination

How-many-distinct-ways-are-there-for-a-knight-to-reach-from-bottom-left-corner-of-chessboard-to-top-right-corner-knight-going-from-square-a1-to-h8-

Question Number 4105 by prakash jain last updated on 28/Dec/15 $$\mathrm{How}\:\mathrm{many}\:\mathrm{distinct}\:\mathrm{ways}\:\mathrm{are}\:\mathrm{there}\:\mathrm{for} \\ $$$$\mathrm{a}\:\mathrm{knight}\:\mathrm{to}\:\mathrm{reach}\:\mathrm{from}\:\mathrm{bottom}\:\mathrm{left}\:\mathrm{corner}\:\mathrm{of} \\ $$$$\mathrm{chessboard}\:\mathrm{to}\:\mathrm{top}\:\mathrm{right}\:\mathrm{corner}. \\ $$$$\left(\mathrm{knight}\:\mathrm{going}\:\mathrm{from}\:\mathrm{square}\:\mathrm{a1}\:\mathrm{to}\:\mathrm{h8}\right). \\ $$ Commented by Filup last updated on…

Prove-that-m-1-n-1-m-2-m-1-n-C-m-m-m-1-n-1-m-m-

Question Number 4103 by prakash jain last updated on 28/Dec/15 $$\mathrm{Prove}\:\mathrm{that} \\ $$$$\underset{{m}=\mathrm{1}} {\overset{{n}} {\sum}}\frac{\left(−\mathrm{1}\right)^{{m}} \:\centerdot\left(\mathrm{2}^{{m}} −\mathrm{1}\right)\:\centerdot\:^{{n}} {C}_{{m}} }{{m}}\:\:=\underset{{m}=\mathrm{1}} {\overset{{n}} {\sum}}\frac{\left(−\mathrm{1}\right)^{{m}} }{{m}} \\ $$ Commented…

Prove-that-there-are-n-r-1-n-1-ways-of-placing-r-identical-objects-in-n-compartments-where-n-gt-r-

Question Number 3884 by Yozzii last updated on 23/Dec/15 $${Prove}\:{that}\:{there}\:{are}\:\begin{pmatrix}{{n}+{r}−\mathrm{1}}\\{{n}−\mathrm{1}}\end{pmatrix}\: \\ $$$${ways}\:{of}\:{placing}\:{r}\:{identical}\:{objects} \\ $$$${in}\:{n}\:{compartments},\:{where}\:{n}>{r}. \\ $$ Commented by RasheedSindhi last updated on 24/Dec/15 $${Let}\:{r}\:{objects}\:{are}\:{denoted}\:{as}\: \\…