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Category: Permutation and Combination

10-couples-are-invited-to-a-dinner-and-should-be-seated-at-a-round-table-in-how-many-ways-can-the-host-do-this-1-generally-2-if-two-men-should-not-sit-next-to-each-other-3-as-2-but-two-spe

Question Number 218299 by mr W last updated on 05/Apr/25 $$\mathrm{10}\:{couples}\:{are}\:{invited}\:{to}\:{a}\:{dinner}\:{and} \\ $$$${should}\:{be}\:{seated}\:{at}\:{a}\:{round}\:{table}. \\ $$$${in}\:{how}\:{many}\:{ways}\:{can}\:{the}\:{host}\:{do} \\ $$$${this}, \\ $$$$\left.\mathrm{1}\right)\:{generally} \\ $$$$\left.\mathrm{2}\right)\:{if}\:{two}\:{men}\:{should}\:{not}\:{sit}\:{next} \\ $$$$\:\:\:\:\:{to}\:{each}\:{other} \\ $$$$\left.\mathrm{3}\left.\right)\:{as}\:\mathrm{2}\right),\:{but}\:{two}\:{speicial}\:{couples}\:…

P-5-6-15-15-6-15-9-15-14-131-2-11-10-9-8-7-6-5-4-3-2-1-9-8-7-6-5-4-3-2-15-14-13-12-11-10-3-603-600-

Question Number 218169 by vile last updated on 31/Mar/25 $${P}\left(\mathrm{5},\mathrm{6}\right)=\frac{\mathrm{15}!}{\left(\mathrm{15}−\mathrm{6}\right)}\:=\:\frac{\mathrm{15}!}{\mathrm{9}!}\: \\ $$$$\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:=\frac{\mathrm{15}×\mathrm{14}×\mathrm{131}×\mathrm{2}×\mathrm{11}×\mathrm{10}×\mathrm{9}×\mathrm{8}×\mathrm{7}×\mathrm{6}×\mathrm{5}×\mathrm{4}×\mathrm{3}×\mathrm{2}×\mathrm{1}}{\mathrm{9}×\mathrm{8}×\mathrm{7}×\mathrm{6}×\mathrm{5}×\mathrm{4}×\mathrm{3}×\mathrm{2}×} \\ $$$$\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:=\mathrm{15}×\mathrm{14}×\mathrm{13}×\mathrm{12}×\mathrm{11}×\mathrm{10} \\ $$$$\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:=\mathrm{3},\mathrm{603},\mathrm{600} \\ $$$$\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\: \\ $$ Terms of Service Privacy Policy…

how-many-different-words-can-be-formed-from-the-word-MATHEMATICS-note-here-a-word-should-have-at-least-two-letters-but-mustn-t-have-a-meaning-

Question Number 218129 by mr W last updated on 30/Mar/25 $${how}\:{many}\:{different}\:{words}\:{can}\:{be} \\ $$$${formed}\:{from}\:{the}\:{word}\: \\ $$$$\boldsymbol{\mathrm{MATHEMATICS}}? \\ $$$${note}:\:\:{here}\:{a}\:{word}\:{should}\:{have}\:{at}\: \\ $$$${least}\:{two}\:{letters},\:{but}\:{mustn}'{t}\:{have}\:{a} \\ $$$${meaning}. \\ $$ Answered by…

Question-213796

Question Number 213796 by efronzo1 last updated on 17/Nov/24 Answered by A5T last updated on 17/Nov/24 $${x}_{\mathrm{0}} ={k}\Rightarrow{x}_{\mathrm{1}} =\frac{\mathrm{1}+{k}}{\mathrm{1}−{k}}\Rightarrow{x}_{\mathrm{2}} =\frac{−\mathrm{1}}{{k}}\Rightarrow{x}_{\mathrm{3}} =\frac{{k}−\mathrm{1}}{\mathrm{1}+{k}}\Rightarrow{x}_{\mathrm{4}} =\frac{\mathrm{2}{k}}{\mathrm{2}}={k} \\ $$$$\Rightarrow{x}_{\mathrm{4}{n}} ={k}=\mathrm{2022}…

in-how-many-ways-can-a-teacher-divide-his-10-studens-into-4-groups-such-that-each-group-has-at-least-2-students-

Question Number 212686 by mr W last updated on 21/Oct/24 $${in}\:{how}\:{many}\:{ways}\:{can}\:{a}\:{teacher} \\ $$$${divide}\:{his}\:\mathrm{10}\:{studens}\:{into}\:\mathrm{4}\:{groups} \\ $$$${such}\:{that}\:{each}\:{group}\:{has}\:{at}\:{least}\:\mathrm{2}\: \\ $$$${students}? \\ $$ Commented by Spillover last updated on…

Find-the-value-of-r-if-10-C-r-10-C-2r-1-

Question Number 209281 by Tawa11 last updated on 06/Jul/24 $$\mathrm{Find}\:\mathrm{the}\:\mathrm{value}\:\mathrm{of}\:\mathrm{r},\:\mathrm{if}\:\:\overset{\mathrm{10}} {\:}\mathrm{C}_{\mathrm{r}} \:\:=\:\:\overset{\mathrm{10}} {\:}\mathrm{C}_{\mathrm{2r}\:\:+\:\:\mathrm{1}} \\ $$ Commented by klipto last updated on 06/Jul/24 $$\:\:\:\:\:\:\:^{\boldsymbol{\mathrm{n}}} \boldsymbol{\mathrm{C}}_{\mathrm{r}} =^{\mathrm{n}}…

n-0-3-n-1-5-n-2-2n-1-n-n-n-1-2-n-2-3-n-3-n-n-n-23-11-n-

Question Number 208662 by efronzo1 last updated on 20/Jun/24 $$\:\:\frac{\begin{pmatrix}{\mathrm{n}}\\{\mathrm{0}}\end{pmatrix}\:+\mathrm{3}\begin{pmatrix}{\mathrm{n}}\\{\mathrm{1}}\end{pmatrix}\:+\mathrm{5}\begin{pmatrix}{\mathrm{n}}\\{\mathrm{2}}\end{pmatrix}\:+…+\left(\mathrm{2n}+\mathrm{1}\right)\begin{pmatrix}{\mathrm{n}}\\{\mathrm{n}}\end{pmatrix}}{\begin{pmatrix}{\mathrm{n}}\\{\mathrm{1}}\end{pmatrix}\:+\mathrm{2}\begin{pmatrix}{\mathrm{n}}\\{\mathrm{2}}\end{pmatrix}\:+\:\mathrm{3}\begin{pmatrix}{\mathrm{n}}\\{\mathrm{3}}\end{pmatrix}\:+…+\mathrm{n}\begin{pmatrix}{\mathrm{n}}\\{\mathrm{n}}\end{pmatrix}}\:=\frac{\mathrm{23}}{\mathrm{11}} \\ $$$$\:\mathrm{n}=? \\ $$ Answered by Berbere last updated on 20/Jun/24 $${A}=\underset{{k}=\mathrm{0}} {\overset{{n}} {\sum}}\left(\mathrm{2}{k}+\mathrm{1}\right)\begin{pmatrix}{{n}}\\{{k}}\end{pmatrix};\underset{{k}=\mathrm{0}} {\overset{{n}}…