## anonymous one year ago How many strings of eight uppercase English letters are there if no letter can be repeated?

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1. zepdrix

I'm taking Combinatorics right now, so I NEED to be able to answer a question like this by next week's test lol grrr, it's giving me some trouble though >.< thinking...

2. zepdrix

|dw:1442540278852:dw|Oh maybe this is simpler than I'm making it. So we have 26 options for the first letter, ya? Any uppercase letter from the English alphabet.

3. zepdrix

Let's say that first letter is an F. Then none of the other following 7 spaces can include an F. Meaning that for our next space we have 25 letters to choose from.|dw:1442540418212:dw|$$\large\rm 26-F=25$$

4. zepdrix

So maybe the next letter is an O. So now we can't include F or O for the remaining places. $$\large\rm 26-F-O=24$$

5. anonymous