I have a question;

What is the probability that a selected letter from the alphabet of 26 letters is selected at random is "either a consonant OR a vowel"?

This was my working out;
21/26 + 5/26 = 1

Is this correct?

Yes very correct

To determine if your working out is correct, let's break down the problem. We can start by calculating the probability of selecting a consonant and the probability of selecting a vowel.

There are 26 letters in the alphabet, and of those, 21 are consonants. To calculate the probability of selecting a consonant, you divide the number of favorable outcomes (21) by the total number of possible outcomes (26). So the probability of selecting a consonant is 21/26.

Similarly, there are 5 vowels in the alphabet. To calculate the probability of selecting a vowel, you divide the number of favorable outcomes (5) by the total number of possible outcomes (26). So the probability of selecting a vowel is 5/26.

Now, to find the probability of selecting either a consonant or a vowel, you add the probabilities of selecting a consonant and selecting a vowel. This is because the events are mutually exclusive, meaning they cannot occur simultaneously.

Therefore, your working out of (21/26) + (5/26) is correct. The sum gives you 26/26, which simplifies to 1.

So the probability of selecting a letter from the alphabet that is either a consonant or a vowel is indeed 1, or 100%.