Category: Permutation and Combination

Question Number 155842 by zainaltanjung last updated on 05/Oct/21 $$\mathrm{Prof}\mathrm{that}:$$$$\underset{\mathrm{n}=1}{\sum ^{10}}\mathrm{n}.\mathrm{n}!=11!-1$$ Commented by puissant last updated on 05/Oct/21 $${Q}\mathrm{155803} \…

Question Number 155356 by qaz last updated on 29/Sep/21 $$\mathrm{Find}\mathrm{the}\mathrm{coefficient}\mathrm{of}\mathrm{term}“{\mathrm{a}}^{\mathrm{m}}{\mathrm{b}}^{2\mathrm{m}}{}^{″}\mathrm{in}{(1+\mathrm{a})}^{\mathrm{m}}{(1+\mathrm{b})}^{\mathrm{n}+\mathrm{m}}{(1+\mathrm{a}+\mathrm{b})}^{\mathrm{m}}.$$ Terms of Service Privacy Policy Contact: info@tinkutara.com

Question Number 155109 by qaz last updated on 25/Sep/21 $$\mathrm{how}\mathrm{many}\mathrm{terms}\mathrm{contain}“{\mathrm{ab}}^2{\mathrm{c}}^3{}^{″}\mathrm{in}{(\mathrm{a}+2\mathrm{b}+3\mathrm{c}+{4\mathrm{d}}^2+{5\mathrm{e}}^3)}^{10}?$$ Answered by mr W last updated on 26/Sep/21…

Question Number 88876 by Joel578 last updated on 13/Apr/20 $$\mathrm{Given}\mathrm{a}10-\mathrm{digit}\mathrm{number}X=1345789026$$$$\mathrm{How}\mathrm{many}10-\mathrm{digit}\mathrm{number}\mathrm{that}\mathrm{can}\mathrm{be}\mathrm{made}$$$$\mathrm{using}\mathrm{every}\mathrm{digit}\mathrm{from}X,\mathrm{with}\mathrm{condition}:$$$$\mathrm{If}\mathrm{a}\mathrm{number}n\mathrm{is}\mathrm{located}\mathrm{in}{k}^{th}\mathrm{position}\mathrm{of}X,\mathrm{then}$$$$\mathrm{the}\mathrm{new}\mathrm{created}\mathrm{number}\mathrm{must}\mathrm{not}\mathrm{contain}$$$$\mathrm{number}n\mathrm{in}{k}^{th}\mathrm{position}$$$$ \…

Question Number 154268 by liberty last updated on 16/Sep/21 Commented by mr W last updated on 16/Sep/21 $$8!=40320$$ Commented by liberty last updated…