unordered/ordered selection from set {1,2,3,4}? Watch

michael_douglas
Badges: 0
#1
Report Thread starter 8 years ago
#1
List all unordered selections of 3 elements from the set {1, 2, 3, 4}.
List also all ordered selections of 3 elements from this set.


i'm not sure what i'm being asked here. is an ordered selection of 3 elements like, {1,2,3} and {2,3,4} where there are 3 elements in order? i've got a feeling there's a lot more to it than that though!

can anyone explain it at all? thank you
0
reply
Hopple
Badges: 16
Rep:
?
#2
Report 8 years ago
#2
You have a funny name for a girl. That or I should point out he's already taken.

You're right about an ordered selection, {1,2,3} is different from {2,3,1}, but they are the same unordered selection.
0
reply
michael_douglas
Badges: 0
#3
Report Thread starter 8 years ago
#3
(Original post by Hopple)
You have a funny name for a girl. That or I should point out he's already taken.

You're right about an ordered selection, {1,2,3} is different from {2,3,1}, but they are the same unordered selection.
heh i'm not a michael douglas fan, it's just a song by neon neon

so the ordered selections would be {1,2,3} and {2,3,4}, and the unordered selections would be {2,3,1}, {3,1,2}, {3,4,2} and {4,2,3}? or am i completely off the mark? thank you!
0
reply
Hopple
Badges: 16
Rep:
?
#4
Report 8 years ago
#4
(Original post by michael_douglas)
heh i'm not a michael douglas fan, it's just a song by neon neon

so the ordered selections would be {1,2,3} and {2,3,4}, and the unordered selections would be {2,3,1}, {3,1,2}, {3,4,2} and {4,2,3}? or am i completely off the mark? thank you!
Wrong way round

Unordered means they are only different if the numbers are different. {1,2,3}={1,3,2} but these are different from {1,2,4}, so in your list of distinct unordered selections, you'd write down {1,2,3},{1,2,4},etc.

Ordered means they are different if the order is different, so in the above example, you would write down all 3 as distinct ordered selections.

Edit: my bad, I just realised what you meant in your first post. An ordered selection is one in which you take note of the elements in it and their order, say like following a recipe. An unordered one is where you only care about what elements are in it, like making a smoothie.
0
reply
michael_douglas
Badges: 0
#5
Report Thread starter 8 years ago
#5
thank you!!
0
reply
X

Quick Reply

Attached files
Write a reply...
Reply
new posts
Latest
My Feed

See more of what you like on
The Student Room

You can personalise what you see on TSR. Tell us a little about yourself to get started.

Personalise

University open days

  • Cardiff Metropolitan University
    Undergraduate Open Day - Llandaff Campus Undergraduate
    Sat, 27 Apr '19
  • University of East Anglia
    Could you inspire the next generation? Find out more about becoming a Primary teacher with UEA… Postgraduate
    Sat, 27 Apr '19
  • Anglia Ruskin University
    Health, Education, Medicine and Social Care; Arts, Humanities and Social Sciences; Business and Law; Science and Engineering Undergraduate
    Sat, 27 Apr '19

Have you registered to vote?

Yes! (551)
37.84%
No - but I will (114)
7.83%
No - I don't want to (102)
7.01%
No - I can't vote (<18, not in UK, etc) (689)
47.32%

Watched Threads

View All
Latest
My Feed