That number is 360, ie
(!4) * 4!6
as reported on that Quora example’s link.
The comb verbs return the number of combinations, not of permutations.
Cheers,
Mike
Please reply to [email protected].
Sent from my iPad
> On 7 Nov 2017, at 22:26, 'Skip Cave' via Programming
> <[email protected]> wrote:
>
> How many four digit numbers can be formed from the number 1,3,4,6,8 and 9 if
> repetition of digits is not allowed?
> <https://www.quora.com/How-many-four-digit-numbers-can-be-formed-from-the-number-1-3-4-6-8-and-9-if-repetition-of-digits-is-not-allowed>
>
> Using Erling's CombE:
>
> b =. 4 CombE 6
>
> a =. 1 3 4 6 8 9
>
> #c = b#a
>
> 15 NB. so the answer is 15.
>
> NB. Convert to decimal
>
> 10 10 10 10#. c
>
> 1346 1348 1349 1368 1369 1389 1468 1469 1489 1689 3468 3469 3489 3689 4689
>
>
> Wait a minute!
>
> What happened to 1364, 1384, 1396, 1436, 1438, 1439, and lots more?
>
> I was hoping CombE would give all combinations of y items taken x at a time
>
>
> Skip
>
>
>
>
>>
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