How many different messages can be transmitted in n microseconds using three different signals…












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How many different messages can be transmitted in n microseconds using three different signals if one signal requires 1 microsecond for transmittal, the other two signals require 2 microseconds each for transmittal, and a signal in a message is followed immediately by the next signal?




I initially got it wrong because I put as the initial condition: $a_0=0, space a_1=1$



I found this solution online:




enter image description here




Why is the initial condition $a_2=3$, and not $a_2=2$? It says the other two signals require $2$ microseconds, so I believe $a_2=2$ because in $2$ microseconds we can only send $2$ signals.










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  • 2




    $begingroup$
    If "A" takes $1$ microsecond and "B" and "C" take $2$, then in $2$ microseconds you can send any of the following: "AA", "B", or "C".
    $endgroup$
    – mjqxxxx
    Apr 21 '14 at 23:00






  • 2




    $begingroup$
    You can also start at $0$ by noting there's exactly one message you can send in $0$ microseconds, namely the empty message (no signal). Then the recursion naturally gives you $a_2=a_1+2a_0=1+2cdot 1=3$.
    $endgroup$
    – celtschk
    Apr 21 '14 at 23:09
















1












$begingroup$



How many different messages can be transmitted in n microseconds using three different signals if one signal requires 1 microsecond for transmittal, the other two signals require 2 microseconds each for transmittal, and a signal in a message is followed immediately by the next signal?




I initially got it wrong because I put as the initial condition: $a_0=0, space a_1=1$



I found this solution online:




enter image description here




Why is the initial condition $a_2=3$, and not $a_2=2$? It says the other two signals require $2$ microseconds, so I believe $a_2=2$ because in $2$ microseconds we can only send $2$ signals.










share|cite|improve this question











$endgroup$








  • 2




    $begingroup$
    If "A" takes $1$ microsecond and "B" and "C" take $2$, then in $2$ microseconds you can send any of the following: "AA", "B", or "C".
    $endgroup$
    – mjqxxxx
    Apr 21 '14 at 23:00






  • 2




    $begingroup$
    You can also start at $0$ by noting there's exactly one message you can send in $0$ microseconds, namely the empty message (no signal). Then the recursion naturally gives you $a_2=a_1+2a_0=1+2cdot 1=3$.
    $endgroup$
    – celtschk
    Apr 21 '14 at 23:09














1












1








1





$begingroup$



How many different messages can be transmitted in n microseconds using three different signals if one signal requires 1 microsecond for transmittal, the other two signals require 2 microseconds each for transmittal, and a signal in a message is followed immediately by the next signal?




I initially got it wrong because I put as the initial condition: $a_0=0, space a_1=1$



I found this solution online:




enter image description here




Why is the initial condition $a_2=3$, and not $a_2=2$? It says the other two signals require $2$ microseconds, so I believe $a_2=2$ because in $2$ microseconds we can only send $2$ signals.










share|cite|improve this question











$endgroup$





How many different messages can be transmitted in n microseconds using three different signals if one signal requires 1 microsecond for transmittal, the other two signals require 2 microseconds each for transmittal, and a signal in a message is followed immediately by the next signal?




I initially got it wrong because I put as the initial condition: $a_0=0, space a_1=1$



I found this solution online:




enter image description here




Why is the initial condition $a_2=3$, and not $a_2=2$? It says the other two signals require $2$ microseconds, so I believe $a_2=2$ because in $2$ microseconds we can only send $2$ signals.







sequences-and-series combinatorics discrete-mathematics






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edited Dec 6 '18 at 18:10







Al Jebr

















asked Apr 21 '14 at 22:43









Al JebrAl Jebr

4,21243276




4,21243276








  • 2




    $begingroup$
    If "A" takes $1$ microsecond and "B" and "C" take $2$, then in $2$ microseconds you can send any of the following: "AA", "B", or "C".
    $endgroup$
    – mjqxxxx
    Apr 21 '14 at 23:00






  • 2




    $begingroup$
    You can also start at $0$ by noting there's exactly one message you can send in $0$ microseconds, namely the empty message (no signal). Then the recursion naturally gives you $a_2=a_1+2a_0=1+2cdot 1=3$.
    $endgroup$
    – celtschk
    Apr 21 '14 at 23:09














  • 2




    $begingroup$
    If "A" takes $1$ microsecond and "B" and "C" take $2$, then in $2$ microseconds you can send any of the following: "AA", "B", or "C".
    $endgroup$
    – mjqxxxx
    Apr 21 '14 at 23:00






  • 2




    $begingroup$
    You can also start at $0$ by noting there's exactly one message you can send in $0$ microseconds, namely the empty message (no signal). Then the recursion naturally gives you $a_2=a_1+2a_0=1+2cdot 1=3$.
    $endgroup$
    – celtschk
    Apr 21 '14 at 23:09








2




2




$begingroup$
If "A" takes $1$ microsecond and "B" and "C" take $2$, then in $2$ microseconds you can send any of the following: "AA", "B", or "C".
$endgroup$
– mjqxxxx
Apr 21 '14 at 23:00




$begingroup$
If "A" takes $1$ microsecond and "B" and "C" take $2$, then in $2$ microseconds you can send any of the following: "AA", "B", or "C".
$endgroup$
– mjqxxxx
Apr 21 '14 at 23:00




2




2




$begingroup$
You can also start at $0$ by noting there's exactly one message you can send in $0$ microseconds, namely the empty message (no signal). Then the recursion naturally gives you $a_2=a_1+2a_0=1+2cdot 1=3$.
$endgroup$
– celtschk
Apr 21 '14 at 23:09




$begingroup$
You can also start at $0$ by noting there's exactly one message you can send in $0$ microseconds, namely the empty message (no signal). Then the recursion naturally gives you $a_2=a_1+2a_0=1+2cdot 1=3$.
$endgroup$
– celtschk
Apr 21 '14 at 23:09










2 Answers
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$begingroup$

Promoting a comment from mjqxxxx to a CW answer



If "A" takes 1 microsecond and "B" and "C" take 2, then in 2 microseconds you can send any of the following: "AA", "B", or "C".






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    $begingroup$

    i found a online solution in which it is showing An = An-1+An-2 because we have two choise here either we can send first signal which 1 second time or we can send another signal which takes two second time anyone of them we can send first so i think the value of A1 = 1 because in 1st second we can send a signal which takes 1 second time and A2 = 1 because in 2 second we cannot send two signal which takes 1 second it is cleared by question so in two second we can send only one signal which takes two second.






    share|cite|improve this answer









    $endgroup$













    • $begingroup$
      It is possible to post mathematical notation, including subscripts and superscripts, using $LaTeX$ syntax with MathJax. See this short introduction and its links to more detailed information.
      $endgroup$
      – hardmath
      Mar 12 '18 at 17:11











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    2 Answers
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    2 Answers
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    $begingroup$

    Promoting a comment from mjqxxxx to a CW answer



    If "A" takes 1 microsecond and "B" and "C" take 2, then in 2 microseconds you can send any of the following: "AA", "B", or "C".






    share|cite|improve this answer











    $endgroup$


















      1












      $begingroup$

      Promoting a comment from mjqxxxx to a CW answer



      If "A" takes 1 microsecond and "B" and "C" take 2, then in 2 microseconds you can send any of the following: "AA", "B", or "C".






      share|cite|improve this answer











      $endgroup$
















        1












        1








        1





        $begingroup$

        Promoting a comment from mjqxxxx to a CW answer



        If "A" takes 1 microsecond and "B" and "C" take 2, then in 2 microseconds you can send any of the following: "AA", "B", or "C".






        share|cite|improve this answer











        $endgroup$



        Promoting a comment from mjqxxxx to a CW answer



        If "A" takes 1 microsecond and "B" and "C" take 2, then in 2 microseconds you can send any of the following: "AA", "B", or "C".







        share|cite|improve this answer














        share|cite|improve this answer



        share|cite|improve this answer








        answered Dec 6 '18 at 4:27


























        community wiki





        Ross Millikan
























            0












            $begingroup$

            i found a online solution in which it is showing An = An-1+An-2 because we have two choise here either we can send first signal which 1 second time or we can send another signal which takes two second time anyone of them we can send first so i think the value of A1 = 1 because in 1st second we can send a signal which takes 1 second time and A2 = 1 because in 2 second we cannot send two signal which takes 1 second it is cleared by question so in two second we can send only one signal which takes two second.






            share|cite|improve this answer









            $endgroup$













            • $begingroup$
              It is possible to post mathematical notation, including subscripts and superscripts, using $LaTeX$ syntax with MathJax. See this short introduction and its links to more detailed information.
              $endgroup$
              – hardmath
              Mar 12 '18 at 17:11
















            0












            $begingroup$

            i found a online solution in which it is showing An = An-1+An-2 because we have two choise here either we can send first signal which 1 second time or we can send another signal which takes two second time anyone of them we can send first so i think the value of A1 = 1 because in 1st second we can send a signal which takes 1 second time and A2 = 1 because in 2 second we cannot send two signal which takes 1 second it is cleared by question so in two second we can send only one signal which takes two second.






            share|cite|improve this answer









            $endgroup$













            • $begingroup$
              It is possible to post mathematical notation, including subscripts and superscripts, using $LaTeX$ syntax with MathJax. See this short introduction and its links to more detailed information.
              $endgroup$
              – hardmath
              Mar 12 '18 at 17:11














            0












            0








            0





            $begingroup$

            i found a online solution in which it is showing An = An-1+An-2 because we have two choise here either we can send first signal which 1 second time or we can send another signal which takes two second time anyone of them we can send first so i think the value of A1 = 1 because in 1st second we can send a signal which takes 1 second time and A2 = 1 because in 2 second we cannot send two signal which takes 1 second it is cleared by question so in two second we can send only one signal which takes two second.






            share|cite|improve this answer









            $endgroup$



            i found a online solution in which it is showing An = An-1+An-2 because we have two choise here either we can send first signal which 1 second time or we can send another signal which takes two second time anyone of them we can send first so i think the value of A1 = 1 because in 1st second we can send a signal which takes 1 second time and A2 = 1 because in 2 second we cannot send two signal which takes 1 second it is cleared by question so in two second we can send only one signal which takes two second.







            share|cite|improve this answer












            share|cite|improve this answer



            share|cite|improve this answer










            answered Mar 12 '18 at 16:19









            Yogesh SinghYogesh Singh

            1




            1












            • $begingroup$
              It is possible to post mathematical notation, including subscripts and superscripts, using $LaTeX$ syntax with MathJax. See this short introduction and its links to more detailed information.
              $endgroup$
              – hardmath
              Mar 12 '18 at 17:11


















            • $begingroup$
              It is possible to post mathematical notation, including subscripts and superscripts, using $LaTeX$ syntax with MathJax. See this short introduction and its links to more detailed information.
              $endgroup$
              – hardmath
              Mar 12 '18 at 17:11
















            $begingroup$
            It is possible to post mathematical notation, including subscripts and superscripts, using $LaTeX$ syntax with MathJax. See this short introduction and its links to more detailed information.
            $endgroup$
            – hardmath
            Mar 12 '18 at 17:11




            $begingroup$
            It is possible to post mathematical notation, including subscripts and superscripts, using $LaTeX$ syntax with MathJax. See this short introduction and its links to more detailed information.
            $endgroup$
            – hardmath
            Mar 12 '18 at 17:11


















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