How much of the total is percentage after a percentage?

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Imagine we have a pie and let $p,q$ be ratios between 0 and 1 (non-inclusive). If I first take $p$ out of the pie, and then $q$ out of the remainder, how much is that of the whole pie?



I can easily visualize that if $p=0.5$ so I take half of the pie, and then take again $q=0.5$ of the remainder, I will have taken a total of 0.75 of the pie. But how do I compute this in general for any $p$ and $q$?







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  • After you take out $p$, how much is left? After you take $q$ of what's left, how much have you taken in total?
    – NickD
    Jul 26 at 19:46














up vote
2
down vote

favorite












Imagine we have a pie and let $p,q$ be ratios between 0 and 1 (non-inclusive). If I first take $p$ out of the pie, and then $q$ out of the remainder, how much is that of the whole pie?



I can easily visualize that if $p=0.5$ so I take half of the pie, and then take again $q=0.5$ of the remainder, I will have taken a total of 0.75 of the pie. But how do I compute this in general for any $p$ and $q$?







share|cite|improve this question



















  • After you take out $p$, how much is left? After you take $q$ of what's left, how much have you taken in total?
    – NickD
    Jul 26 at 19:46












up vote
2
down vote

favorite









up vote
2
down vote

favorite











Imagine we have a pie and let $p,q$ be ratios between 0 and 1 (non-inclusive). If I first take $p$ out of the pie, and then $q$ out of the remainder, how much is that of the whole pie?



I can easily visualize that if $p=0.5$ so I take half of the pie, and then take again $q=0.5$ of the remainder, I will have taken a total of 0.75 of the pie. But how do I compute this in general for any $p$ and $q$?







share|cite|improve this question











Imagine we have a pie and let $p,q$ be ratios between 0 and 1 (non-inclusive). If I first take $p$ out of the pie, and then $q$ out of the remainder, how much is that of the whole pie?



I can easily visualize that if $p=0.5$ so I take half of the pie, and then take again $q=0.5$ of the remainder, I will have taken a total of 0.75 of the pie. But how do I compute this in general for any $p$ and $q$?









share|cite|improve this question










share|cite|improve this question




share|cite|improve this question









asked Jul 26 at 19:36









advanced_learner

132




132











  • After you take out $p$, how much is left? After you take $q$ of what's left, how much have you taken in total?
    – NickD
    Jul 26 at 19:46
















  • After you take out $p$, how much is left? After you take $q$ of what's left, how much have you taken in total?
    – NickD
    Jul 26 at 19:46















After you take out $p$, how much is left? After you take $q$ of what's left, how much have you taken in total?
– NickD
Jul 26 at 19:46




After you take out $p$, how much is left? After you take $q$ of what's left, how much have you taken in total?
– NickD
Jul 26 at 19:46










1 Answer
1






active

oldest

votes

















up vote
2
down vote



accepted










The rule you want is
$$
pq
$$
when you take fraction $p$ and then fraction $q$ of what you just took.



In your problem you take $p$ of the pie and then $q$ from what's left over so your total is
$$
p + (1-p)q .
$$






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    1 Answer
    1






    active

    oldest

    votes








    1 Answer
    1






    active

    oldest

    votes









    active

    oldest

    votes






    active

    oldest

    votes








    up vote
    2
    down vote



    accepted










    The rule you want is
    $$
    pq
    $$
    when you take fraction $p$ and then fraction $q$ of what you just took.



    In your problem you take $p$ of the pie and then $q$ from what's left over so your total is
    $$
    p + (1-p)q .
    $$






    share|cite|improve this answer



























      up vote
      2
      down vote



      accepted










      The rule you want is
      $$
      pq
      $$
      when you take fraction $p$ and then fraction $q$ of what you just took.



      In your problem you take $p$ of the pie and then $q$ from what's left over so your total is
      $$
      p + (1-p)q .
      $$






      share|cite|improve this answer

























        up vote
        2
        down vote



        accepted







        up vote
        2
        down vote



        accepted






        The rule you want is
        $$
        pq
        $$
        when you take fraction $p$ and then fraction $q$ of what you just took.



        In your problem you take $p$ of the pie and then $q$ from what's left over so your total is
        $$
        p + (1-p)q .
        $$






        share|cite|improve this answer















        The rule you want is
        $$
        pq
        $$
        when you take fraction $p$ and then fraction $q$ of what you just took.



        In your problem you take $p$ of the pie and then $q$ from what's left over so your total is
        $$
        p + (1-p)q .
        $$







        share|cite|improve this answer















        share|cite|improve this answer



        share|cite|improve this answer








        edited Jul 26 at 19:54


























        answered Jul 26 at 19:43









        Ethan Bolker

        35.7k54199




        35.7k54199






















             

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