Determine the number of ways that two letters can be selected from {A, B, C, D} if the order in the sample is not to be considered.

List the possible samples.

N = 4C2

N = 6 ways

List of samples;

1. A, B

2. A, C

3. A, D

4. B, C

5. B, D

6. C, D

Step-by-step explanation:

Since the order is not relevant, this is a combination case.

nCr = n!/r! (n-r) !

We are to select two letters from A, B, C, D (2 from 4)

The number of possible selections N can be given as:

N = 4C2 = 4!/2! (4-2) ! = 4!/2!2! = 6

N = 6 ways

List of samples;

1. A, B

2. A, C

3. A, D

4. B, C

5. B, D

6. C, D