How many different four letter code words can be formed using the letters A, B, C, and D?

Question

The options are: 

 

1. 16

2. 24

3. 64

4. 120

5. 204

6. 256

7. 308

Answer 1

If a letter can be used more than once, then the number of possibilities is (4)(4)(4)(4) = 4⁴ = 256

 

If each letter is used only once, then the number of possibilities is (4)(3)(2)(1) = 24

Answer 2

if there is repetition...

there are 4 letters, all different

4*4*4*4=256

if there is no repetition...

4*3*2*1=24

this is a permutation, not a combination