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So far Johnny has received the grades: $5$, $3$, $3$, $3$, $2$, $2$, $1$, $1$, for the math course in this school term. What another grade he needs to get so that the average of grades is lower than $2.5$? (Assumption: All grades are of the same weight in grading scale of $1$, $2$, $3$, $4$, $5$, where $1$ is the best result.)