If I have 4 quarters and I need a 60% to pass the school year what equation can I use to find what I need to pass?
Example. 1st marking period: 87.20% 2nd marking period 69.15% 3rd marking period: 45.92%. What would the equation be to find out what I need for the 4th quarter for my gpa to be above 60%
On
let $a,b,c,d$ be the grades that you get in the 4 quarters. $a$ is the mark that you get for the first quarter, $b$ for the second , .... etc.
Now let $x,y,z,e$ be the total marks for each of the quarters . $x$ is the total mark for the first quarter, $y$ is the total mark for the second quarter , etc.
Now you need $$\frac{a + b + c +d}{x+y+z+e} \geq 0.6$$
and for your example, you need $$\frac{87.2 + 69.15 + 45.92 + m}{4} \geq 60\%$$ and so $$ m = 60\times 4 - (87.2 + 69.15 + 45.92) = 37.73 \%$$ to pass
Assuming equal weights and passing from $0-100\%$ to $0-1$, we must solve: $$\frac{0.872 + 0.6915+0.4592+x}{4}\geq 0.6$$This yields $x =0.3773$, that is, you'd need $37.73\%$ to pass.