Amanda’s teacher calculates grades using a weighted average. she counts homework as 10%, quizzes as 15%, projects as 20%, tests as 40%, and the final exam as 15% of the final grade. going into the final, amanda has scores of 90 for homework, 75 for quizzes, 76 for projects, and 80 for tests. what grade does amanda need on the final exam if she wants to get an overall grade of at least an 80?

Amanda needs a grade of at least 83 2/3 on her final exam

Amanda's grade (g) is calculated from her homework grade (h), quiz grade (q), project grade (p), test grade (t), and final grade (f) using the formula ...

... g = 0.10h +0.15q +0.20p +0.40t +0.15f

Amanda wants g ≥ 80.

Filling in the values, we have ...

... 0.10·90 +0.15·75 +0.20·76 +0.40·80 +0.15·f ≥ 80

... 9 + 11.25 + 15.20 + 32 + 0.15f ≥ 80 . . . . . simplify a bit

... 0.15f ≥ 80 -67.45 . . . . . . . . . . . . . . . . . . . . subtract 67.45

... f ≥ 12.55/0.15 . . . . . . . . . . . . . . . . . . . . . . . divide by the coefficient of f

... f ≥ 83 2/3

3/6   and 9/18

step-by-step explanation: