# Math

posted by
**John**
.

how many three letter security codes can be made from 4 letters A,B,C,D without using a letter twice? For example, BAC and A,D,B are two such codes. Explain

posted by
**John**
.

how many three letter security codes can be made from 4 letters A,B,C,D without using a letter twice? For example, BAC and A,D,B are two such codes. Explain