Something I never learned in math class..

[djheater]

...and neither does she, I told her the math geeks on ATOT would probably know it...

My daughter is trying to figure out how many combinations of 3 numbers = twelve.

She's 8 and obviously smarter than her parents.

PS - hevnsnt and DarkKnight69 she's looking for total possible permutations.

PPS - Sorry Goosemaster... addition only...yes I realize that's important, but I'm dumb.

 

[hevnsnt]

1+1+10

 

[User1001]

n/m

 

[DarkKnight69]

1-2-9
3-5-4
7-3-2

 

[Goosemaster]

combinations? addition? subtraction? single digits?

 

[hevnsnt]

2-4-6

 

[mundane]

Are we talking only positive integers? Real or natural numbers?

 

[Ferocious]

n/m
I misread.

 

[Goosemaster]

Originally posted by: diegoalcatraz
Are we talking only positive integers? Real or natural numbers?

exactly

 

[djheater]

Originally posted by: Goosemaster

Originally posted by: diegoalcatraz
Are we talking only positive integers? Real or natural numbers?

exactly

Sorry, but really I didn't give it nearly enough thought...

I'm certain she meant addition, I'd ask but she's asleep of course... and I imagine her limit was numerals up to 12... and limited to three digits so 10+1+1 is valid but 12+0+0 isn't.

 

[Ferocious]

I took probability a hundred years ago, but I'll take a stab...

(12^3)/ 6

 

[akubi]

you need to specify if the order matters or not. i.e., is 1+1+10 counted differently from 1+10+1 or 10+1+1

if order does matter, then it's 11 choose 2 = 55.

but I think you are asking for the case in which order doesn't matter (so 1+1+10, 1+10+1, 10+1+1 are all treated as one solution)

in that case you need to consider the three cases.

a) all three numbers are the same (4,4,4)
b) two numbers are the same (1,1,10)
c) all three numbers are different (1,2,9)

a happens only once.
b happens 4*3 times in the order matters count. cuz four (1,1 2,2, 3,3 5,5) pairs times 3 permutation possible each.
so c happens (55-1-4*3)/6 times = 7.

1+4+7 = 12.

you can also list out all the cases to get 12.