Question 1143455
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<pre>
You need to solve this inequality


    80 <= {{{(77 + 63 + 92 + 78 + x)/5}}} < 90.


I will do it step by step :


    5*80 <= 77 + 63 + 92 + 78 + x  < 5*90

    400  <= 310 + x < 450

    400 - 310 <= x < 450 - 310

    90 <= x < 140.


But the value of x is restricted from the above by 100 automatically (= by the definition (!) ), so the 


<U>ANSWER</U> is : the student must get any grade equal or greater than 90.
</pre>

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Another closely related question, &nbsp;which left aside, &nbsp;is "what is the maximum mean grade the student can reach ?"



The answer is  &nbsp;&nbsp;{{{(77+63+92+78+100)/5}}} = {{{410/5}}} = 92.