Probability of flood.












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$begingroup$


I was solving a question of probability and the question was " If the probability of occurrence of flood in any year is 1/20 then what is probability that flood will occur in 3rd year exactly?
This is easy to solve and the answer that I got is 361/8000. But then one question strikes my mind what if exactly is not written? What if we need to find the probability that flood will occur in 3rd year?
On the previous question my approach was 19/20 × 19/20 × 1/20. But I am sure that this can not be applied to latter question. I think this will be solved by probability distribution however I am not sure about this. If anyone know how to solve this please provide guidance.










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    1












    $begingroup$


    I was solving a question of probability and the question was " If the probability of occurrence of flood in any year is 1/20 then what is probability that flood will occur in 3rd year exactly?
    This is easy to solve and the answer that I got is 361/8000. But then one question strikes my mind what if exactly is not written? What if we need to find the probability that flood will occur in 3rd year?
    On the previous question my approach was 19/20 × 19/20 × 1/20. But I am sure that this can not be applied to latter question. I think this will be solved by probability distribution however I am not sure about this. If anyone know how to solve this please provide guidance.










    share|cite|improve this question











    $endgroup$















      1












      1








      1





      $begingroup$


      I was solving a question of probability and the question was " If the probability of occurrence of flood in any year is 1/20 then what is probability that flood will occur in 3rd year exactly?
      This is easy to solve and the answer that I got is 361/8000. But then one question strikes my mind what if exactly is not written? What if we need to find the probability that flood will occur in 3rd year?
      On the previous question my approach was 19/20 × 19/20 × 1/20. But I am sure that this can not be applied to latter question. I think this will be solved by probability distribution however I am not sure about this. If anyone know how to solve this please provide guidance.










      share|cite|improve this question











      $endgroup$




      I was solving a question of probability and the question was " If the probability of occurrence of flood in any year is 1/20 then what is probability that flood will occur in 3rd year exactly?
      This is easy to solve and the answer that I got is 361/8000. But then one question strikes my mind what if exactly is not written? What if we need to find the probability that flood will occur in 3rd year?
      On the previous question my approach was 19/20 × 19/20 × 1/20. But I am sure that this can not be applied to latter question. I think this will be solved by probability distribution however I am not sure about this. If anyone know how to solve this please provide guidance.







      probability probability-distributions






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      edited Jan 11 at 9:02







      Kishan Thacker

















      asked Jan 11 at 7:36









      Kishan ThackerKishan Thacker

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      214






















          2 Answers
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          $begingroup$

          In any year the probability is $frac1{20}$, so also for the $3$rd year.






          share|cite|improve this answer









          $endgroup$





















            1












            $begingroup$

            First of all, in your previous computation your approach is correct but the result is wrong:
            $$19/20 cdot 19/20 cdot 1/20=frac{361}{8000}.$$
            As regards your variation, if you would like to evaluate the probability that the flood occurs within the third year, i.e. the first year or the second year or the third year, then it should be:
            $$1/20+(19/20cdot 1/20)+(19/20 cdot 19/20 cdot 1/20)=frac{1141}{8000}.$$
            Note that the probability that the flood occurs the third year (we remove the word "exactly"), or any other year, is just $1/20$.






            share|cite|improve this answer











            $endgroup$













            • $begingroup$
              Sorry 381 was typing error. That has been corrected.
              $endgroup$
              – Kishan Thacker
              Jan 11 at 8:07










            • $begingroup$
              I am bit embarrassed about the question as just now I realised that I was puzzeled after altering the question. And the answer to my altered question was none other then 1/20 itself. 😥
              $endgroup$
              – Kishan Thacker
              Jan 11 at 8:11










            • $begingroup$
              I think you have misunderstood my question I think 1141/8000 is probability of occurrence of flood exaxactly on 1st or exactly on 2nd or exactly on 3rd year.
              $endgroup$
              – Kishan Thacker
              Jan 11 at 8:13










            • $begingroup$
              Yes if you simply remove the word "exactly" the probability is $1/20$. If you mean within the third year then it is $1141/8000$
              $endgroup$
              – Robert Z
              Jan 11 at 8:20










            • $begingroup$
              BTW your correction is not complete: it is $361/8000$ not $361/800$.
              $endgroup$
              – Robert Z
              Jan 11 at 8:23











            Your Answer





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            2 Answers
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            active

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            2 Answers
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            0












            $begingroup$

            In any year the probability is $frac1{20}$, so also for the $3$rd year.






            share|cite|improve this answer









            $endgroup$


















              0












              $begingroup$

              In any year the probability is $frac1{20}$, so also for the $3$rd year.






              share|cite|improve this answer









              $endgroup$
















                0












                0








                0





                $begingroup$

                In any year the probability is $frac1{20}$, so also for the $3$rd year.






                share|cite|improve this answer









                $endgroup$



                In any year the probability is $frac1{20}$, so also for the $3$rd year.







                share|cite|improve this answer












                share|cite|improve this answer



                share|cite|improve this answer










                answered Jan 11 at 8:21









                drhabdrhab

                103k545136




                103k545136























                    1












                    $begingroup$

                    First of all, in your previous computation your approach is correct but the result is wrong:
                    $$19/20 cdot 19/20 cdot 1/20=frac{361}{8000}.$$
                    As regards your variation, if you would like to evaluate the probability that the flood occurs within the third year, i.e. the first year or the second year or the third year, then it should be:
                    $$1/20+(19/20cdot 1/20)+(19/20 cdot 19/20 cdot 1/20)=frac{1141}{8000}.$$
                    Note that the probability that the flood occurs the third year (we remove the word "exactly"), or any other year, is just $1/20$.






                    share|cite|improve this answer











                    $endgroup$













                    • $begingroup$
                      Sorry 381 was typing error. That has been corrected.
                      $endgroup$
                      – Kishan Thacker
                      Jan 11 at 8:07










                    • $begingroup$
                      I am bit embarrassed about the question as just now I realised that I was puzzeled after altering the question. And the answer to my altered question was none other then 1/20 itself. 😥
                      $endgroup$
                      – Kishan Thacker
                      Jan 11 at 8:11










                    • $begingroup$
                      I think you have misunderstood my question I think 1141/8000 is probability of occurrence of flood exaxactly on 1st or exactly on 2nd or exactly on 3rd year.
                      $endgroup$
                      – Kishan Thacker
                      Jan 11 at 8:13










                    • $begingroup$
                      Yes if you simply remove the word "exactly" the probability is $1/20$. If you mean within the third year then it is $1141/8000$
                      $endgroup$
                      – Robert Z
                      Jan 11 at 8:20










                    • $begingroup$
                      BTW your correction is not complete: it is $361/8000$ not $361/800$.
                      $endgroup$
                      – Robert Z
                      Jan 11 at 8:23
















                    1












                    $begingroup$

                    First of all, in your previous computation your approach is correct but the result is wrong:
                    $$19/20 cdot 19/20 cdot 1/20=frac{361}{8000}.$$
                    As regards your variation, if you would like to evaluate the probability that the flood occurs within the third year, i.e. the first year or the second year or the third year, then it should be:
                    $$1/20+(19/20cdot 1/20)+(19/20 cdot 19/20 cdot 1/20)=frac{1141}{8000}.$$
                    Note that the probability that the flood occurs the third year (we remove the word "exactly"), or any other year, is just $1/20$.






                    share|cite|improve this answer











                    $endgroup$













                    • $begingroup$
                      Sorry 381 was typing error. That has been corrected.
                      $endgroup$
                      – Kishan Thacker
                      Jan 11 at 8:07










                    • $begingroup$
                      I am bit embarrassed about the question as just now I realised that I was puzzeled after altering the question. And the answer to my altered question was none other then 1/20 itself. 😥
                      $endgroup$
                      – Kishan Thacker
                      Jan 11 at 8:11










                    • $begingroup$
                      I think you have misunderstood my question I think 1141/8000 is probability of occurrence of flood exaxactly on 1st or exactly on 2nd or exactly on 3rd year.
                      $endgroup$
                      – Kishan Thacker
                      Jan 11 at 8:13










                    • $begingroup$
                      Yes if you simply remove the word "exactly" the probability is $1/20$. If you mean within the third year then it is $1141/8000$
                      $endgroup$
                      – Robert Z
                      Jan 11 at 8:20










                    • $begingroup$
                      BTW your correction is not complete: it is $361/8000$ not $361/800$.
                      $endgroup$
                      – Robert Z
                      Jan 11 at 8:23














                    1












                    1








                    1





                    $begingroup$

                    First of all, in your previous computation your approach is correct but the result is wrong:
                    $$19/20 cdot 19/20 cdot 1/20=frac{361}{8000}.$$
                    As regards your variation, if you would like to evaluate the probability that the flood occurs within the third year, i.e. the first year or the second year or the third year, then it should be:
                    $$1/20+(19/20cdot 1/20)+(19/20 cdot 19/20 cdot 1/20)=frac{1141}{8000}.$$
                    Note that the probability that the flood occurs the third year (we remove the word "exactly"), or any other year, is just $1/20$.






                    share|cite|improve this answer











                    $endgroup$



                    First of all, in your previous computation your approach is correct but the result is wrong:
                    $$19/20 cdot 19/20 cdot 1/20=frac{361}{8000}.$$
                    As regards your variation, if you would like to evaluate the probability that the flood occurs within the third year, i.e. the first year or the second year or the third year, then it should be:
                    $$1/20+(19/20cdot 1/20)+(19/20 cdot 19/20 cdot 1/20)=frac{1141}{8000}.$$
                    Note that the probability that the flood occurs the third year (we remove the word "exactly"), or any other year, is just $1/20$.







                    share|cite|improve this answer














                    share|cite|improve this answer



                    share|cite|improve this answer








                    edited Jan 11 at 8:24

























                    answered Jan 11 at 8:01









                    Robert ZRobert Z

                    99.8k1068140




                    99.8k1068140












                    • $begingroup$
                      Sorry 381 was typing error. That has been corrected.
                      $endgroup$
                      – Kishan Thacker
                      Jan 11 at 8:07










                    • $begingroup$
                      I am bit embarrassed about the question as just now I realised that I was puzzeled after altering the question. And the answer to my altered question was none other then 1/20 itself. 😥
                      $endgroup$
                      – Kishan Thacker
                      Jan 11 at 8:11










                    • $begingroup$
                      I think you have misunderstood my question I think 1141/8000 is probability of occurrence of flood exaxactly on 1st or exactly on 2nd or exactly on 3rd year.
                      $endgroup$
                      – Kishan Thacker
                      Jan 11 at 8:13










                    • $begingroup$
                      Yes if you simply remove the word "exactly" the probability is $1/20$. If you mean within the third year then it is $1141/8000$
                      $endgroup$
                      – Robert Z
                      Jan 11 at 8:20










                    • $begingroup$
                      BTW your correction is not complete: it is $361/8000$ not $361/800$.
                      $endgroup$
                      – Robert Z
                      Jan 11 at 8:23


















                    • $begingroup$
                      Sorry 381 was typing error. That has been corrected.
                      $endgroup$
                      – Kishan Thacker
                      Jan 11 at 8:07










                    • $begingroup$
                      I am bit embarrassed about the question as just now I realised that I was puzzeled after altering the question. And the answer to my altered question was none other then 1/20 itself. 😥
                      $endgroup$
                      – Kishan Thacker
                      Jan 11 at 8:11










                    • $begingroup$
                      I think you have misunderstood my question I think 1141/8000 is probability of occurrence of flood exaxactly on 1st or exactly on 2nd or exactly on 3rd year.
                      $endgroup$
                      – Kishan Thacker
                      Jan 11 at 8:13










                    • $begingroup$
                      Yes if you simply remove the word "exactly" the probability is $1/20$. If you mean within the third year then it is $1141/8000$
                      $endgroup$
                      – Robert Z
                      Jan 11 at 8:20










                    • $begingroup$
                      BTW your correction is not complete: it is $361/8000$ not $361/800$.
                      $endgroup$
                      – Robert Z
                      Jan 11 at 8:23
















                    $begingroup$
                    Sorry 381 was typing error. That has been corrected.
                    $endgroup$
                    – Kishan Thacker
                    Jan 11 at 8:07




                    $begingroup$
                    Sorry 381 was typing error. That has been corrected.
                    $endgroup$
                    – Kishan Thacker
                    Jan 11 at 8:07












                    $begingroup$
                    I am bit embarrassed about the question as just now I realised that I was puzzeled after altering the question. And the answer to my altered question was none other then 1/20 itself. 😥
                    $endgroup$
                    – Kishan Thacker
                    Jan 11 at 8:11




                    $begingroup$
                    I am bit embarrassed about the question as just now I realised that I was puzzeled after altering the question. And the answer to my altered question was none other then 1/20 itself. 😥
                    $endgroup$
                    – Kishan Thacker
                    Jan 11 at 8:11












                    $begingroup$
                    I think you have misunderstood my question I think 1141/8000 is probability of occurrence of flood exaxactly on 1st or exactly on 2nd or exactly on 3rd year.
                    $endgroup$
                    – Kishan Thacker
                    Jan 11 at 8:13




                    $begingroup$
                    I think you have misunderstood my question I think 1141/8000 is probability of occurrence of flood exaxactly on 1st or exactly on 2nd or exactly on 3rd year.
                    $endgroup$
                    – Kishan Thacker
                    Jan 11 at 8:13












                    $begingroup$
                    Yes if you simply remove the word "exactly" the probability is $1/20$. If you mean within the third year then it is $1141/8000$
                    $endgroup$
                    – Robert Z
                    Jan 11 at 8:20




                    $begingroup$
                    Yes if you simply remove the word "exactly" the probability is $1/20$. If you mean within the third year then it is $1141/8000$
                    $endgroup$
                    – Robert Z
                    Jan 11 at 8:20












                    $begingroup$
                    BTW your correction is not complete: it is $361/8000$ not $361/800$.
                    $endgroup$
                    – Robert Z
                    Jan 11 at 8:23




                    $begingroup$
                    BTW your correction is not complete: it is $361/8000$ not $361/800$.
                    $endgroup$
                    – Robert Z
                    Jan 11 at 8:23


















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