SOLUTION: With a view to estimating how many fish there are in a big lake, 25,000 fish are tagged and then released. After some time 20,000 fish are captured and it is found that 50 of the

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Question 1193840: With a view to estimating how many fish there are in a big lake, 25,000 fish are tagged and then released.
After some time 20,000 fish are captured and it is found that 50 of them are tagged.
Give an estimate of the number of fish in the lake.
50/20000= 1/400
25000 * 1/400= 10 000 000

Found 2 solutions by josgarithmetic, ikleyn:
Answer by josgarithmetic(39616)   (Show Source): You can put this solution on YOUR website!
That 20000 fish to be captured again is a very large number compared to the original number first estimated to be in the lake.
Answer by ikleyn(52776)   (Show Source): You can put this solution on YOUR website!
.
With a view to estimating how many fish there are in a big lake, 25,000 fish are tagged and then released.
After some time 20,000 fish are captured and it is found that 50 of them are tagged.
Give an estimate of the number of fish in the lake.
50/20000= 1/400
25000 * 1/400= 10 000 000
~~~~~~~~~~~~~~~

To give an estimate, we write this proportion

     = ,


where X is the number of fish in the lake (total) which we want to estimate.


This proportion express a very natural assumption that all tagged and released fish 
are uniformly distributed among all other fish in the lake.


From the proportion, we get  X =  = 10,000,000.    ANSWER

Solved and explained.

---------------

On proportions,  see the lessons
    - Proportions
    - Using proportions to solve word problems
    - Using proportions to solve word problems in Physics
    - Using proportions to solve Chemistry problems
    - Using proportions to estimate the number of fish in a lake (*)
    - HOW TO algebreze and solve these problems using proportions
    - OVERVIEW of lessons on proportions
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