Respuesta :
As given that first 5grades are: 71%, 82%, 71%, 78% and 78%.
Let the 6th grade be C
a). Then:
[tex]75\leq\frac{71+82+71+78+78+C}{6}\leq80[/tex]Simplifying it:
[tex]\begin{gathered} 75\leq\frac{71+82+71+78+78+C}{6} \\ 75\times6\leq380+C \\ 450\leq380+C \\ 450-380\leq C \\ 70\leq C \end{gathered}[/tex]And:
[tex]\begin{gathered} \frac{380+C}{6}\leq80 \\ 380+C\leq480 \\ C\leq100 \end{gathered}[/tex]So C should be in between 70 to 100.
b). For at least 80%:
[tex]\begin{gathered} \frac{71+82+71+78+78+C}{6}\ge80 \\ 380+C\ge80\times6 \\ 380+C\ge480 \\ C\ge100 \end{gathered}[/tex]It is not possible for getting b grade as one cannot achieve more than maximum marks if the maximum marks are 100.
