Category: Permutation and Combination

Question Number 177597 by cortano1 last updated on 07/Oct/22 Answered by mr W last updated on 07/Oct/22 $$\mathit{m}\mathit{e}\mathit{t}\mathit{h}\mathit{o}\mathit{d}1:\mathit{w}\mathit{i}\mathit{t}\mathit{h}\mathit{o}\mathit{u}\mathit{t}\mathit{u}\mathit{s}\mathit{i}\mathit{n}\mathit{g}\mathit{f}\mathit{o}\mathit{r}\mathit{m}\mathit{u}\mathit{l}\mathit{a}$$$$1\times 1\times C_3^6\times 2^3$$$$+\left[\mathrm{1}×\left(−\mathrm{1}\right)+\mathrm{3}×\mathrm{1}\right]×{C}_{\mathrm{2}} ^{\mathrm{6}}…

Question Number 111906 by mr W last updated on 05/Sep/20 Answered by PRITHWISH SEN 2 last updated on 22/Sep/20 $$\mathrm{Disarrangement}\mathrm{of}6\mathrm{cards}!6=265$$$$\mathrm{now}\mathrm{in}\mathrm{this}265\mathrm{ways}\mathrm{card}\mathrm{no}.1\mathrm{can}\mathrm{be}\mathrm{in}$$$$\mathrm{envelope}\:\mathrm{no}.\:\mathrm{2},\mathrm{3},\mathrm{4},\mathrm{5}\:\mathrm{or}\:\mathrm{6}\:\mathrm{and}\:\mathrm{in}\:\mathrm{each}\:\mathrm{case}\:\mathrm{the} \…

Question Number 111732 by Aina Samuel Temidayo last updated on 04/Sep/20 $$\mathrm{A}\mathrm{blind}\mathrm{man}\mathrm{is}\mathrm{to}\mathrm{place}5\mathrm{letters}\mathrm{into}5$$$$\mathrm{pigeon}\mathrm{holes},\mathrm{how}\mathrm{many}\mathrm{ways}\mathrm{can}4\mathrm{of}$$$$\mathrm{the}\mathrm{letters}\mathrm{be}\mathrm{wrongly}\mathrm{placed}?$$$$(\mathrm{note}\mathrm{that}\mathrm{only}\mathrm{one}\mathrm{letter}\mathrm{must}\mathrm{be}\mathrm{in}\mathrm{a}$$$$\mathrm{pigeon}\mathrm{hole})$$ Answered by mr…

Question Number 177040 by cortano1 last updated on 30/Sep/22 Answered by mr W last updated on 30/Sep/22 $$totalnumberof9-digitnumbersis:$$$$9!=362880$$$$$$$${number}\:{of}\:{those}\:{which}\:{are}\:{divisible} \…

Question Number 177007 by Ar Brandon last updated on 29/Sep/22 Answered by mr W last updated on 29/Sep/22 $$1.hebuysthe{13}^{th}floor:$$$${12}^{th}floorisalsobought.tobuythe$$$${rest}\:\mathrm{6}\:{floors}\:{there}\:{are}\:{C}_{\mathrm{6}}…