In dire need of help!!(data management)

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peeweegary

peeweegary

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GTP_peeweegary, peeweegary
Well, i have been trying to solve these two problems for literally an hour. I'm so stuck on this question and now i turn to GTP for help:dopey:.

A palindrome is a sequence of letters such as MADAM, which remainds unchanged when the order of the letters is reversed. How many five letter palindromes are possible...
a)if a letter may appear more than once?
b)if a letter may not be used more than twice

This is from a worksheet entitled permutations and combinations, so it would be best if you geniuses to use one of the methods. The answers to a is 17576 and b is 15600.

Thanks in advance:)
 
peeweegary
Well, i have been trying to solve these two problems for literally an hour. I'm so stuck on this question and now i turn to GTP for help:dopey:.

A palindrome is a sequence of letters such as MADAM, which remainds unchanged when the order of the letters is reversed. How many five letter palindromes are possible...
a)if a letter may appear more than once?
b)if a letter may not be used more than twice

This is from a worksheet entitled permutations and combinations, so it would be best if you geniuses to use one of the methods. The answers to a is 17576 and b is 15600.

Thanks in advance:)
Click to expand...

Well, I got the answers but my process is probably a little off.

For #1 I just did 26*26*26. You have 26 choices for the first and last letter, 26 choices for the 2nd and 4th, and 26 for the 3rd letter. Since they can repeat you can choose from 26 letters and get things like just 5 A's.

For #2 I did 26*25*24, which is also 26 nPr 3. Once you choose a letter for the first and last places, you have 25 left for the 2nd and 4th and then 24 to choose from for the 3rd spot.
 

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