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Category: Permutation and Combination

How-many-three-digit-numbers-can-be-formed-using-the-digits-2-3-5-7-8-if-the-number-is-odd-and-no-digit-is-repeted-

Question Number 153714 by pete last updated on 09/Sep/21 $$\mathrm{How}\:\mathrm{many}\:\mathrm{three}−\mathrm{digit}\:\mathrm{numbers}\:\mathrm{can}\:\mathrm{be} \\ $$$$\mathrm{formed}\:\mathrm{using}\:\mathrm{the}\:\mathrm{digits}\:\mathrm{2},\mathrm{3},\mathrm{5},\mathrm{7},\mathrm{8}\:\mathrm{if}\: \\ $$$$\mathrm{the}\:\mathrm{number}\:\mathrm{is}\:\mathrm{odd}\:\mathrm{and}\:\mathrm{no}\:\mathrm{digit}\:\mathrm{is}\:\mathrm{repeted}? \\ $$ Answered by EDWIN88 last updated on 09/Sep/21 $$=\:{P}_{\mathrm{1}} ^{\:\mathrm{3}}…

How-many-handshakes-are-exchanged-betwen-27-boys-

Question Number 87790 by mathocean1 last updated on 06/Apr/20 $$\mathrm{How}\:\mathrm{many}\:\mathrm{handshakes}\:\mathrm{are}\:\mathrm{exchanged} \\ $$$$\mathrm{betwen}\:\mathrm{27}\:\mathrm{boys}? \\ $$ Answered by TANMAY PANACEA. last updated on 06/Apr/20 $$\mathrm{27}{C}_{\mathrm{2}} \\ $$$$=\frac{\mathrm{27}!}{\mathrm{2}!\mathrm{25}!}=\frac{\mathrm{27}×\mathrm{26}}{\mathrm{2}}=\mathrm{351}…

in-how-many-ways-can-the-number-n-be-written-as-a-sum-of-three-positive-integers-if-representations-differing-in-the-order-of-the-terms-are-considered-to-be-different-

Question Number 153220 by talminator2856791 last updated on 05/Sep/21 $$\: \\ $$$$\:\mathrm{in}\:\mathrm{how}\:\mathrm{many}\:\mathrm{ways}\:\mathrm{can}\:\mathrm{the}\:\mathrm{number}\:\: \\ $$$$\:{n}\:\mathrm{be}\:\mathrm{written}\:\mathrm{as}\:\mathrm{a}\:\mathrm{sum}\:\mathrm{of}\:\mathrm{three}\:\mathrm{positive}\:\: \\ $$$$\:\mathrm{integers}\:\mathrm{if}\:\mathrm{representations}\:\mathrm{differing}\:\: \\ $$$$\:\mathrm{in}\:\mathrm{the}\:\mathrm{order}\:\mathrm{of}\:\mathrm{the}\:\mathrm{terms}\:\mathrm{are}\:\mathrm{considered}\:\: \\ $$$$\:\mathrm{to}\:\mathrm{be}\:\mathrm{different}?\:\: \\ $$$$\: \\ $$ Answered…