How many 3 letter arrangements can you make while making the first and the third letter one of the 21 constants and the middle letter one of the 5 vowels {a,e,i,o,u} . {two such arrangments to use are KOM and XAX?

From your example I can see that repetition is allowed so

21*5*21 = ...

To find the number of 3-letter arrangements with the specified conditions, we need to consider the number of choices for each position.

In this case, we have:
- 21 options for the first letter (constants)
- 5 options for the middle letter (vowels)
- 21 options for the third letter (constants)

To calculate the total number of arrangements, we simply multiply the number of choices for each position together:

Total number of arrangements = Number of choices for first letter * Number of choices for middle letter * Number of choices for third letter

Total number of arrangements = 21 * 5 * 21

Now, let's calculate the answer:

Total number of arrangements = 2205

Therefore, there are a total of 2205 different 3-letter arrangements that can be made using one of the 21 constants for the first and third positions, and one of the 5 vowels for the middle position.