Online Course Discussion Forum
Math Challenge IC Handout 6
There are a few confusing points in the homework. For 6.18, I don't think we would be able to mathematically calculate that, we would have to look into a dictionary and manually count it. In 6.22, what are Martian words?
Thank you!
Think of a "word" as a sequence of letters (even if it is not possible to read in English). The words in 6.18 will only have $A$' and $B$'s, for example $AABBBABAB$.
The first part of problem 6.22 was missing on the online homework. The problem should say "Suppose the Martian alphabet has 10 letters, and a Martian word is any sequence of 4 letters, allowing repeats.". It has now been corrected on the homework.
Thanks! I tried the Martian question but I don't know what to do when it allows repeats. I tried to do the "n choose r" method but realized it doesn't work in this case. Then I tried the permutation with order method and the results are still too small. Then I tried multiplying 10 for 10 letters to those results and it made no sense. I started thinking about the nonrepeated lettered words + "10 choose 2" times 2! + "10 choose 2" times"8 choose 2" + "10 choose 3" times"7 choose 1" + "10 choose 4" but it didn't make any sense to me.
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