Quantcast

Got Homework?

Connect with other students for help. It's a free community.

  • across
    MIT Grad Student
    Online now
  • laura*
    Helped 1,000 students
    Online now
  • Hero
    College Math Guru
    Online now

Here's the question you clicked on:

55 members online
  • 0 replying
  • 0 viewing

vishal_kothari Group Title

Seven people are in an elevator which stops at ten floors. In how many ways can they get o the elevator...

  • 2 years ago
  • 2 years ago

  • This Question is Closed
  1. vishal_kothari Group Title
    Best Response
    You've already chosen the best response.
    Medals 10

    get*off*the

    • 2 years ago
  2. nubeer Group Title
    Best Response
    You've already chosen the best response.
    Medals 0

    not sure maybe 10! x 7!

    • 2 years ago
  3. vishal_kothari Group Title
    Best Response
    You've already chosen the best response.
    Medals 10

    no..

    • 2 years ago
  4. FoolForMath Group Title
    Best Response
    You've already chosen the best response.
    Medals 3

    \( 11^7 \) ?

    • 2 years ago
  5. vishal_kothari Group Title
    Best Response
    You've already chosen the best response.
    Medals 10

    no..

    • 2 years ago
  6. FoolForMath Group Title
    Best Response
    You've already chosen the best response.
    Medals 3

    what is the answer ?

    • 2 years ago
  7. FoolForMath Group Title
    Best Response
    You've already chosen the best response.
    Medals 3

    @across: I don't think that's the right answer.

    • 2 years ago
  8. vishal_kothari Group Title
    Best Response
    You've already chosen the best response.
    Medals 10

    (a) 7^10 (b) 10^7

    • 2 years ago
  9. vishal_kothari Group Title
    Best Response
    You've already chosen the best response.
    Medals 10

    answer lies between this two...

    • 2 years ago
  10. FoolForMath Group Title
    Best Response
    You've already chosen the best response.
    Medals 3

    answer is \( 10^7 \) then.

    • 2 years ago
  11. AnwarA Group Title
    Best Response
    You've already chosen the best response.
    Medals 0

    Oh, I think the answer that across gave assumed that each one gets off in a different floor?

    • 2 years ago
  12. vishal_kothari Group Title
    Best Response
    You've already chosen the best response.
    Medals 10

    how?

    • 2 years ago
  13. FoolForMath Group Title
    Best Response
    You've already chosen the best response.
    Medals 3

    The problem is modeled as " how many ways can n distinct object can be divided in r distinct groups " some groups may be empty.

    • 2 years ago
  14. FoolForMath Group Title
    Best Response
    You've already chosen the best response.
    Medals 3

    My earlier answer assumes the super-set and I over counted few other cases.

    • 2 years ago
  15. across Group Title
    Best Response
    You've already chosen the best response.
    Medals 0

    FFM is correct.

    • 2 years ago
  16. vishal_kothari Group Title
    Best Response
    You've already chosen the best response.
    Medals 10

    ya..

    • 2 years ago
  17. across Group Title
    Best Response
    You've already chosen the best response.
    Medals 0

    Think of it in smaller terms: suppose there are three floors and two people; they can get off the elevator in 9 different ways, which is \(3^2\) as FFM's model states.\[\]

    • 2 years ago
  18. FoolForMath Group Title
    Best Response
    You've already chosen the best response.
    Medals 3

    Precisely, my earlier answer assumes that the seven people need not to get off the elevator at all and only some of them get down and all of the other obvious cases.

    • 2 years ago
  19. FoolForMath Group Title
    Best Response
    You've already chosen the best response.
    Medals 3

    @across: wanna try a variation " atleast one should get off in each floor" ? ; )

    • 2 years ago
  20. vishal_kothari Group Title
    Best Response
    You've already chosen the best response.
    Medals 10

    ok..

    • 2 years ago
  21. across Group Title
    Best Response
    You've already chosen the best response.
    Medals 0

    In this case, though, there are more floors than there are people. :p

    • 2 years ago
  22. FoolForMath Group Title
    Best Response
    You've already chosen the best response.
    Medals 3

    @vishal kothari: It's a bit hard, don't attempt it if you don't need it.

    • 2 years ago
  23. FoolForMath Group Title
    Best Response
    You've already chosen the best response.
    Medals 3

    @across: well just increase the numbers :P

    • 2 years ago
  24. across Group Title
    Best Response
    You've already chosen the best response.
    Medals 0

    Let's try 7 floors and 10 people.

    • 2 years ago
  25. FoolForMath Group Title
    Best Response
    You've already chosen the best response.
    Medals 3

    or more generally any \( r \gt n \)

    • 2 years ago
  26. FoolForMath Group Title
    Best Response
    You've already chosen the best response.
    Medals 3

    Sorry it should be: or more generally any \( r<n \) pertaining to my above model.

    • 2 years ago
  27. across Group Title
    Best Response
    You've already chosen the best response.
    Medals 0

    Whoops.

    • 2 years ago
  28. FoolForMath Group Title
    Best Response
    You've already chosen the best response.
    Medals 3

    @across: Sorry, that doesn't seem correct, as \( n^{ \underline{r} } \) is not the correct assumption, generally people attempt it with mutual inclusion-exclusion, but there is a even clever way, If you want I can give you a hint but it would be probably a spoiler.

    • 2 years ago
  29. pokemon23 Group Title
    Best Response
    You've already chosen the best response.
    Medals 1

    anyone willing to explain me about square roots?

    • 2 years ago
  30. FoolForMath Group Title
    Best Response
    You've already chosen the best response.
    Medals 3

    Anyways, always excuse my solecism :P

    • 2 years ago
  31. robtobey Group Title
    Best Response
    You've already chosen the best response.
    Medals 0

    Assume that the elevator riders are considered indistinguishable, for example, 7 warm bodies. There are 11440 ways for them to get off of an elevator servicing 10 floors. http://2000clicks.com/mathhelp/CountingObjectsInBoxes.aspx Refer to: Indistinguishable Objects to Distinguishable Boxes The number of different ways to distribute n indistinguishable balls into k distinguishable boxes is C(n+k-1,k-1). For those who have access to Mathematica the following is a user defined function called Elevator where r is the number of riders and f is the number of floors. Elevator[ r_ , f_ ] := Binomial[ r + f - 1, f - 1]

    • 2 years ago
    • Attachments:

See more questions >>>

Your question is ready. Sign up for free to start getting answers.

spraguer (Moderator)
5 → View Detailed Profile

is replying to Can someone tell me what button the professor is hitting...

23

  • Teamwork 19 Teammate
  • Problem Solving 19 Hero
  • You have blocked this person.
  • ✔ You're a fan Checking fan status...

Thanks for being so helpful in mathematics. If you are getting quality help, make sure you spread the word about OpenStudy.

This is the testimonial you wrote.
You haven't written a testimonial for Owlfred.