How many two-letter combonations can be made using only the letters A,B,C, and D? Double letters are allowed. AB is not considered the same as BA. Explain please!
2006-12-08 10:11:11 · 7 answers · asked by kjhglkhg 2 in Science & Mathematics ➔ Mathematics
=> 4 letters : A,B,C,D with repetitions
Imagine 2 boxes (box #1 and box #2) : UU
double letters are allowed => aa,bb,cc,dd = 4 combinations (A)
ab not equal to ba => we can't repeat combinations
We put 4 letters inside the box #1 and
we can put only 3 letters inside the box #2.
So, we obtain 4 x 3 = 12 combinations (B)
(A) + (B) = 12 + 4 = 16 combinations. (Answer)
2006-12-08 11:08:37 · answer #1 · answered by frank 7 · 1⤊ 0⤋
12 if each letter can only be used once in a combo. if you have "a" then there are only 3 other letters that can make the combonations with "a" in front and since there are 4 letters you take 4 x 3 to get 12
2006-12-08 18:21:44 · answer #2 · answered by blueb_24 2 · 0⤊ 0⤋
it is a problem of permutation without repetition
the total is (4)! / (4-2)! = 12
however, you can double the letters, so it has to be four more choices, so the final result is 12 + 4 = 16
2006-12-08 18:41:51 · answer #3 · answered by James Chan 4 · 0⤊ 0⤋
4 choices for each letter so there are 4*4=16 possibilities.
2006-12-08 22:49:05 · answer #4 · answered by yupchagee 7 · 0⤊ 0⤋
aa ab ac ad ba bb bc bd ca cb cc cd da db dc dd 16 different combinations
2006-12-08 18:15:11 · answer #5 · answered by rocky 1 · 2⤊ 0⤋
AB
AC
AD That is what I got..not sure if it is much help
BA
BC
BD
CA
CB
CD
2006-12-08 18:15:28 · answer #6 · answered by marymojo2002 2 · 1⤊ 0⤋
aa
ab
ac
ad
ba
bb
bc
bd
ca
cb
cc
cd
ea
eb
ec
ed
i think?
2006-12-08 18:18:36 · answer #7 · answered by ~HOT bebe~ 2 · 0⤊ 0⤋