Question 1177971
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<pre>

Let  d  be "in how many days . . . ".


Then you have this proportion


    {{{6_rats/(3_cats*9_days)}}} = {{{12_rats/(9_cats*d_days)}}},    (1)

or

    {{{6/(3*9)}}} = {{{12/(9d)}}}.     (1)

    {{{6/27}}} = {{{12/(9d)}}}.


The proportion says that the rate  {{{rats/(cats*days)}}} is the same in both cases.


From proportion  (1),  you have


    9d = {{{(12*27)/6}}} = 2*27

     d = {{{(2*27)/9}}} = 2*3 = 6 days.      <U>AMSWER</U>
</pre>

Solved.


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