Respuesta :
Answer:
To obtain a "B", Rita needs to score between 76.7 and 100.
Step-by-step explanation:
Chapter tests mean:
[tex]M = \frac{70 + 76 + 86 + 87 + 85}{5} = 80.8[/tex]
Grades:
80.8 worth 60% = 0.6
85 worth 10% = 0.1
x worth 0.3.
So her grade is:
[tex]G = 80.8*0.6 + 85*0.1 + 0.3x = 56.98 + 0.3x[/tex]
What scores can Rita earn on the final exam to earn a "B" in the course if the cut-off for a "B" is an overall score greater than or equal to 80, but less than 90?
G has to be greater than or equal to 80 and less than 90, so:
[tex]80 \leq G < 90[/tex]
Lower bound:
[tex]G \geq 80[/tex]
[tex]56.98 + 0.3x \geq 80[/tex]
[tex]0.3x \geq 80 - 56.98[/tex]
[tex]x \geq \frac{80 - 56.98}{0.3}[/tex]
[tex]x \geq 76.7[/tex]
Upper bound:
[tex]G < 90[/tex]
[tex]56.98 + 0.3x < 80[/tex]
[tex]0.3x < 90 - 56.98[/tex]
[tex]x < \frac{90 - 56.98}{0.3}[/tex]
[tex]x < 110[/tex]
Highest grade is 100, so:
To obtain a "B", Rita needs to score between 76.7 and 100.
