how many combinations of 5 numbers are there from 7 numbers

[revpat55]

Can anyone tell me how many combinations of 5 there are from 7 numbers - I think it's 28 but I don't know where I got that from. Any bright sparks with the answer for me (and more importantly, what ARE the combinations or where can I find them on the internet!)

[bednobs]

it must be many many more than 28.

[dr b]

It should be 21 = 7!/(5! x (7-5)!).

(where 7! = 7 x 6 x 5 x 4 x 3 x 2 x 1, etc.) This assumes order of numbers doesn't matter (1-2-3-4-5 = 5-4-3-2-1)

1 2 3 4 5
1 2 3 4 6
1 2 3 4 7
1 2 3 5 6
1 2 3 5 7
1 2 3 6 7
1 2 4 5 6
1 2 4 5 7
1 2 4 6 7
1 2 5 6 7
1 3 4 5 6
1 3 4 5 7
1 3 4 6 7
1 3 5 6 7
1 4 5 6 7
2 3 4 5 6
2 3 4 5 7
2 3 4 6 7
2 3 5 6 7
2 4 5 6 7
3 4 5 6 7

[factor-fiction]

i agree with dr b </> provided (as he/she says) the order of the numbers doesn't matter.

[revpat55]

brilliant - its nice to see it worked out in front of you, I got myself so confused!! Many thanks