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Category: Permutation and Combination

Question-118555

Question Number 118555 by bramlexs22 last updated on 18/Oct/20 Answered by benjo_mathlover last updated on 18/Oct/20 $${Start}\:{with}\:{the}\:\mathrm{4}\:{non}−{red}\:{slots},\:{then}\:{we} \\ $$$${have}\:\begin{pmatrix}{\mathrm{5}}\\{\mathrm{2}}\end{pmatrix}\:{ways}\:{in}\:{which}\:{we}\:{can}\:{assigned}\:{of} \\ $$$${inserting}\:{the}\:{red}\:{slots}\:{to}\:{get}\:{a}\:{sequence}\:{of} \\ $$$$\mathrm{8}\:{categorised}\:{slots}\:{where}\:{the}\:{red}\:{slots}\: \\ $$$${are}\:{all}\:{apart}\:.\:{So}\:{the}\:{number}\:{of}\:{ways}\:{is}\:…

1-solve-the-equation-x-49-50-x-50-49-49-x-50-50-x-49-2-How-many-numbers-from-12-to-12345-inclusive-have-digits-which-are-consecutive-an-in-increasing-order-reading

Question Number 118489 by bramlexs22 last updated on 18/Oct/20 $$\left(\mathrm{1}\right)\:{solve}\:{the}\:{equation}\:\frac{{x}−\mathrm{49}}{\mathrm{50}}\:+\:\frac{{x}−\mathrm{50}}{\mathrm{49}}\:=\:\frac{\mathrm{49}}{{x}−\mathrm{50}}\:+\:\frac{\mathrm{50}}{{x}−\mathrm{49}} \\ $$$$\left(\mathrm{2}\right)\:{How}\:{many}\:{numbers}\:{from}\:\mathrm{12}\:{to}\:\mathrm{12345}\: \\ $$$${inclusive}\:{have}\:{digits}\:{which}\:{are}\: \\ $$$${consecutive}\:{an}\:{in}\:{increasing}\:{order}, \\ $$$${reading}\:{from}\:{left}\:{to}\:{right}\:?\: \\ $$ Answered by benjo_mathlover last updated…

If-all-the-words-with-or-without-meaning-are-written-using-the-letters-of-the-word-QUEEN-and-are-arranged-as-in-English-dictionary-What-is-the-position-of-the-word-QUEEN-a-44th-b-45th-c-46th-d-47th-

Question Number 52381 by Necxx last updated on 07/Jan/19 $${If}\:{all}\:{the}\:{words}\:{with}\:{or}\:{without} \\ $$$${meaning}\:{are}\:{written}\:{using}\:{the} \\ $$$${letters}\:{of}\:{the}\:{word}\:{QUEEN}\:{and} \\ $$$${are}\:{arranged}\:{as}\:{in}\:{English} \\ $$$${dictionary}.{What}\:{is}\:{the}\:{position} \\ $$$${of}\:{the}\:{word}\:{QUEEN}? \\ $$$$\left.{a}\left.\right)\left.\mathrm{4}\left.\mathrm{4}{th}\:{b}\right)\mathrm{45}{th}\:{c}\right)\mathrm{46}{th}\:{d}\right)\mathrm{47}{th} \\ $$ Answered…

The-sum-of-the-digits-in-the-unit-place-of-all-four-digit-numbers-formed-using-the-numbers-3-4-5-andL-6-without-repetition-is-a-432-b-108-c-36-d-18-

Question Number 52379 by Necxx last updated on 07/Jan/19 $${The}\:{sum}\:{of}\:{the}\:{digits}\:{in}\:{the}\:{unit} \\ $$$${place}\:{of}\:{all}\:{four}\:{digit}\:{numbers} \\ $$$${formed}\:{using}\:{the}\:{numbers}\:\mathrm{3}\:\mathrm{4}\:\mathrm{5}\:{and}\mathscr{L} \\ $$$$\mathrm{6}\:{without}\:{repetition}\:{is} \\ $$$$\left.{a}\left.\right)\left.\mathrm{4}\left.\mathrm{32}\:{b}\right)\mathrm{108}\:{c}\right)\mathrm{36}\:{d}\right)\mathrm{18} \\ $$ Answered by tanmay.chaudhury50@gmail.com last updated…

8-digit-numbers-are-formed-using-1-1-2-2-2-3-4-4-The-number-of-such-numbers-in-which-the-odd-digits-do-not-occupy-odd-places-is-a-160-b-120-c-60-d-48-

Question Number 52278 by Necxx last updated on 05/Jan/19 $$\mathrm{8}\:{digit}\:{numbers}\:{are}\:{formed}\:{using} \\ $$$$\mathrm{1}\:\mathrm{1}\:\mathrm{2}\:\mathrm{2}\:\mathrm{2}\:\mathrm{3}\:\mathrm{4}\:\mathrm{4}.\:{The}\:{number}\:{of}\:{such} \\ $$$${numbers}\:{in}\:{which}\:{the}\:{odd}\:{digits} \\ $$$${do}\:{not}\:{occupy}\:{odd}\:{places}\:{is} \\ $$$$\left.{a}\left.\right)\left.\mathrm{1}\left.\mathrm{60}\:{b}\right)\mathrm{120}\:{c}\right)\mathrm{60}\:{d}\right)\mathrm{48} \\ $$ Answered by tanmay.chaudhury50@gmail.com last updated…

An-8-digit-number-divisible-by-9-is-to-be-formed-using-digits-from-0-to-9-without-repeating-the-digits-The-number-of-ways-in-which-this-can-be-done-is-a-72-7i-b-18-7i-c-40-7i-d-36-7i-please-I-m

Question Number 52276 by Necxx last updated on 05/Jan/19 $${An}\:\mathrm{8}\:{digit}\:{number}\:{divisible}\:{by}\:\mathrm{9}\:{is} \\ $$$${to}\:{be}\:{formed}\:{using}\:{digits}\:{from} \\ $$$$\mathrm{0}\:{to}\:\mathrm{9}\:{without}\:{repeating}\:{the}\:{digits}. \\ $$$${The}\:{number}\:{of}\:{ways}\:{in}\:{which}\:{this} \\ $$$${can}\:{be}\:{done}\:{is}? \\ $$$$\left.{a}\left.\right)\left.\mathrm{7}\left.\mathrm{2}\left(\mathrm{7}{i}\right)\:{b}\right)\mathrm{18}\left(\mathrm{7}{i}\right)\:{c}\right)\mathrm{40}\left(\mathrm{7}{i}\right)\:{d}\right)\mathrm{36}\left(\mathrm{7}{i}\right) \\ $$$$ \\ $$$${please}\:{I}\:{mean}\:\boldsymbol{{factorial}}\:{by}\:{i}.{The} \\…

Find-the-number-of-all-5-digit-numbers-x-1-x-2-x-3-x-4-x-5-with-x-1-x-2-x-3-x-4-x-5-

Question Number 117708 by mr W last updated on 13/Oct/20 $${Find}\:{the}\:{number}\:{of}\:{all}\:\mathrm{5}\:{digit} \\ $$$${numbers}\:{x}_{\mathrm{1}} {x}_{\mathrm{2}} {x}_{\mathrm{3}} {x}_{\mathrm{4}} {x}_{\mathrm{5}} \:{with} \\ $$$${x}_{\mathrm{1}} \geqslant{x}_{\mathrm{2}} \geqslant{x}_{\mathrm{3}} \geqslant{x}_{\mathrm{4}} \geqslant{x}_{\mathrm{5}} .…

Q-In-how-many-ways-8-students-can-be-divided-into-two-equal-groups-Ans-8-2-4-2-here-why-two-factorial-is-divided-we-do-not-do-the-same-incase-of-distributing-52-cards-equally-

Question Number 51779 by aseerimad last updated on 30/Dec/18 $${Q}=\:\:{In}\:{how}\:{many}\:{ways}\:\mathrm{8}\:{students}\:{can}\:{be}\:{divided}\:{into}\:{two}\:{equal}\:{groups}? \\ $$$$ \\ $$$${Ans}=\:\:\:\:\frac{\mathrm{8}!}{\mathrm{2}!×\left(\mathrm{4}!\right)^{\mathrm{2}} }\:\:\: \\ $$$$ \\ $$$${here}\:{why}\:{two}\:{factorial}\:{is}\:{divided}? \\ $$$${we}\:{do}\:{not}\:{do}\:{the}\:{same}\:{incase}\:{of}\:{distributing}\:\mathrm{52}\:{cards}\:{equally}\:{among}\:\mathrm{4}\:{persons}. \\ $$$$ \\ $$$${pls}\:{explain}……

In-how-many-different-ways-can-we-select-5-numbers-from-9-numbers-1-2-3-9-A-number-may-be-selected-more-than-one-time-

Question Number 117281 by mr W last updated on 10/Oct/20 $${In}\:{how}\:{many}\:{different}\:{ways}\:{can}\:{we} \\ $$$${select}\:\mathrm{5}\:{numbers}\:{from}\:\mathrm{9}\:{numbers} \\ $$$$\left\{\mathrm{1},\mathrm{2},\mathrm{3},…,\mathrm{9}\right\}?\: \\ $$$${A}\:{number}\:{may}\:{be}\:{selected}\:{more}\:{than} \\ $$$${one}\:{time}. \\ $$ Answered by PRITHWISH SEN…