Hello everyone. I'm not sure where to begin with this problem becuase I don't think I know what they are trying to tell me.(adsbygoogle = window.adsbygoogle || []).push({});

Heres what it says:

In morse code, Symobls are represented by variable-length sequences of dots and dashes. For example, A = .-, 1 = . - - - -, ? = . . - - . .

How many different symobls can be represented by sequences of seven or fewwer dots and dashes?

So are they saying, I have a total number of 7 either dots or dashes to work with and how many different permutations can i get with that? or how many different combinations can i get with that?

Order shouldn't matter, they didn't say it did, and also repeitions not allowed becuase you don't want 2, A's, ?'s, etc.

So that leaves me to think its combinations.

Would this be correct?

combinations formula is the following:

Choosing r items from n possibilities:

n!/[r! (n-r)!]

so your choose 2 items from 7 possibilities

r = 2

n = 7

7!/[2!5!] = 21 different symbols can be represeented by sequences of seven or fewer dots and dashes.

**Physics Forums | Science Articles, Homework Help, Discussion**

Join Physics Forums Today!

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

# I'm not sure I understand the problem, can someone clarify?

**Physics Forums | Science Articles, Homework Help, Discussion**