Question 1171613
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<pre>

Let n be the number of donuts required.


The wording description, translated to Math, leads to this equation


    {{{(10000 + 0.15n)/n}}} = 3.00    (average cost).


From this equation


    10000 + 0.15n = 3n,  or

    10000 = 3n - 0.15n

    10000 = (3-0.15)n

    10000 = 2.85n

      n   = 10000/2.85 = 3508.77 = 3509 (rounded to closest greater integer).    <U>ANSWER</U>
</pre>

Solved.