All of you mathematical wizards-

All of you mathematical wizards-

Posers and Puzzles

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Dave

S.Yorks.England

Joined
18 Apr 10
Moves
83883
26 Dec 21

We had a question in an xmas quiz which is really easy to work out "longhand" but maybe there's a quick way of doing it with a formula:-
In the 12 days of xmas, how many gifts were given in total?
(1*12, 2*11 3*10 etc.)
No Saturday paper this week by the way

Secret RHP coder

on the payroll

Joined
26 Nov 04
Moves
155080
26 Dec 21

@venda said
We had a question in an xmas quiz which is really easy to work out "longhand" but maybe there's a quick way of doing it with a formula:-
In the 12 days of xmas, how many gifts were given in total?
(1*12, 2*11 3*10 etc.)
No Saturday paper this week by the way
Wouldn't that be a sum?

As in 1+2+...+11+12 = 78

G

Joined
16 Aug 15
Moves
1245
26 Dec 21

@bigdogg said
Wouldn't that be a sum?

As in 1+2+...+11+12 = 78
I think you and I talked about this before. To add 1-100 you can
101x50
So
13x6=78

E

Joined
12 Jul 08
Moves
13814
26 Dec 21
1 edit

With a series this short does it really matter?

Dave

S.Yorks.England

Joined
18 Apr 10
Moves
83883
26 Dec 21

That's not the question.It's the accumulative gifts as in the song.
I.e on the 1st day a partridge = 1
2nd day 2 turtle doves and a partridge = 3 gifts
3rd day 3 french hens 2 turtle doves and a partridge = 6 gifts and so on

E

Joined
12 Jul 08
Moves
13814
27 Dec 21
1 edit

@venda said
That's not the question.It's the accumulative gifts as in the song.
I.e on the 1st day a partridge = 1
2nd day 2 turtle doves and a partridge = 3 gifts
3rd day 3 french hens 2 turtle doves and a partridge = 6 gifts and so on
It is just 1+2+3+4+5+6+7+8+9+10+11+12.

One day 2, 3 gifts were not given. On day 2 only 2 gifts were given.

She did not get 12 partridges and 12 pear trees.

Of course day 1 may actually count as 2 gifts.

Secret RHP coder

on the payroll

Joined
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Moves
155080
27 Dec 21

@venda

In that case, here's the best I can do.

[1*12 + 2*11 + 3*10 + 4*9 + 5*8 + 6*7] * 2
(sequence obviously repeats)

[1*6 + 1*11 + 3*5 + 2*9 + 5*4 + 3*7] * 4
(divide every term inside braces by 2; change outer term to 4)

[6 + 11 + 18 + 36 + 20] * 4
(multiply out small terms)

91 * 4 = 364

Secret RHP coder

on the payroll

Joined
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27 Dec 21

Found a very nice solution here:

https://www.intmath.com/blog/mathematics/the-twelve-days-of-christmas-how-many-presents-1686

The page derives a formula that works for any number of days. In this case, n=12.

Formula: (n/6)(n+1)(n+2) = number of gifts


But does it really work?
(12/6)*13*14 = 364 -- yup

Dave

S.Yorks.England

Joined
18 Apr 10
Moves
83883
27 Dec 21
1 edit

@bigdogg said
Found a very nice solution here:

https://www.intmath.com/blog/mathematics/the-twelve-days-of-christmas-how-many-presents-1686

The page derives a formula that works for any number of days. In this case, n=12.

[hidden]Formula: (n/6)(n+1)(n+2) = number of gifts[/hidden]

But does it really work?
[hidden](12/6)*13*14 = 364 -- yup[/hidden]
Excellent Mr Dogg
That is what I was after
But how is the 6 derived?

Secret RHP coder

on the payroll

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27 Dec 21

@venda said
Excellent Mr Dogg
That is what I was after
But how is the 6 derived?
The article explains that in the "General Formula" section.

Misfit Queen

Isle of Misfit Toys

Joined
08 Aug 03
Moves
36705
29 Dec 21

@eladar said
It is just 1+2+3+4+5+6+7+8+9+10+11+12.

One day 2, 3 gifts were not given. On day 2 only 2 gifts were given.

She did not get 12 partridges and 12 pear trees.

Of course day 1 may actually count as 2 gifts.
Maybe you should give the song another listen.



[Verse 1]
On the first day of Christmas, my true love sent to me
A partridge in a pear tree

[Verse 2]
On the second day of Christmas, my true love sent to me
Two turtle doves, and
A partridge in a pear tree

[Verse 3]
On the third day of Christmas, my true love sent to me
Three french hens
Two turtle doves, and
A partridge in a pear tree

[Verse 4]
On the fourth day of Christmas, my true love sent to me
Four calling birds
Three french hens
Two turtle doves, and
A partridge in a pear tree

[Verse 5]
On the fifth day of Christmas, my true love sent to me
Five golden rings
Four calling birds
Three french hens
Two turtle doves, and
A partridge in a pear tree

[Verse 6]
On the sixth day of Christmas, my true love sent to me
Six geese a-laying
Five golden rings
Four calling birds
Three french hens
Two turtle doves, and
A partridge in a pear tree

[Verse 7]
On the seventh day of Christmas, my true love sent to me
Seven swans a-swimming
Six geese a-laying
Five golden rings
Four calling birds
Three french hens
Two turtle doves, and
A partridge in a pear tree

[Verse 8]
On the eighth day of Christmas, my true love sent to me
Eight maids a-milking
Seven swans a-swimming
Six geese a-laying
Five golden rings
Four calling birds
Three french hens
Two turtle doves, and
A partridge in a pear tree

[Verse 9]
On the ninth day of Christmas, my true love sent to me
Nine ladies dancing
Eight maids a-milking
Seven swans a-swimming
Six geese a-laying
Five golden rings
Four calling birds
Three french hens
Two turtle doves, and
A partridge in a pear tree

[Verse 10]
On the tenth day of Christmas, my true love sent to me
Ten lords a-leaping
Nine ladies dancing
Eight maids a-milking
Seven swans a-swimming
Six geese a-laying
Five golden rings
Four calling birds
Three french hens
Two turtle doves, and
A partridge in a pear tree

[Verse 11]
On the eleventh day of Christmas, my true love sent to me
Eleven pipers piping
Ten lords a-leaping
Nine ladies dancing
Eight maids a-milking
Seven swans a-swimming
Six geese a-laying
Five golden rings
Four calling birds
Three french hens
Two turtle doves, and
A partridge in a pear tree

[Verse 12]
On the twelfth day of Christmas, my true love sent to me
Twelve drummers drumming
Eleven pipers piping
Ten lords a-leaping
Nine ladies dancing
Eight maids a-milking
Seven swans a-swimming
Six geese a-laying
Five golden rings
Four calling birds
Three french hens
Two turtle doves, and
A partridge in a pear tree

Big Dogg's equation is exactly correct.

Dave

S.Yorks.England

Joined
18 Apr 10
Moves
83883
29 Dec 21

@suzianne said
Maybe you should give the song another listen.

[youtube]9ZL1u-0Tycc[/youtube]

[Verse 1]
On the first day of Christmas, my true love sent to me
A partridge in a pear tree

[Verse 2]
On the second day of Christmas, my true love sent to me
Two turtle doves, and
A partridge in a pear tree

[Verse 3]
On the third day of Christmas, my true love sent to me
Three fr ...[text shortened]... h hens
Two turtle doves, and
A partridge in a pear tree

Big Dogg's equation is exactly correct.
It wasn't necessary to paste the song.It depends how you interpret the grammar.
The gift sequence is repeated every day for the sake of the (may I say very monotonous)song and suggests the gifts were repeated
If not,why doesn't the song simply state the days gift instead of repeating:-
On the second day my true love gave to me 2 Doves
On the 3rd day my true love gave to me 3 hens and so on.
The point of my post was to find a formula for ANY total in an accumulative sequence which is what big dogg did.
If you substitute any number into the equation for the 12 the formula works negating the necessity to multiply 1*12,2*11 etc and adding them up, and so can be used for other purposes in Mathematics other than a pointless song.
Elegant

s
Fast and Curious

slatington, pa, usa

Joined
28 Dec 04
Moves
53223
01 Jan 22

@venda
Well for us folkies, the song is there as a test of memory, all that stuff in the right order and such.

I don't sing much myself, wife does that, I just do instrumentals, guitar, mandolin and the like.

I guess it would be REALLY boring if it was just an instrumental🙂

E

Joined
12 Jul 08
Moves
13814
01 Jan 22
1 edit

@venda said
It wasn't necessary to paste the song.It depends how you interpret the grammar.
The gift sequence is repeated every day for the sake of the (may I say very monotonous)song and suggests the gifts were repeated
If not,why doesn't the song simply state the days gift instead of repeating:-
On the second day my true love gave to me 2 Doves
On the 3rd day my true love gave to me ...[text shortened]... them up, and so can be used for other purposes in Mathematics other than a pointless song.
Elegant
https://www.clickondetroit.com/news/2021/12/10/how-much-do-the-12-days-of-christmas-actually-cost/


This is the only place I have ever seen anyone suggest there were actually 12 pear trees given.

But hey, any level of idiocy is accepted as truth around here.

s
Fast and Curious

slatington, pa, usa

Joined
28 Dec 04
Moves
53223
01 Jan 22

@Eladar
Yep, you should know ALL about pushing fake BS.