I need a mathematical percentage for a final exam grade, too see how many points I need for a $90\%$ average.

Question

I have a math exam tomorrow. My current overall-average is $98\%$(A). The exam will be $15$ OR $20\%$ of the final grade. What percentage would I need on this exam to get at least $90\%$ (A-) as a final year grade?

The calculation I think for $20\%$ looks like this:

$(0.80 \cdot 98)+(0.20 \cdot x)=90$

I calculated this equation for both $20$ and $15\%$, but I get for $20\%$ a smaller amount than for $15\%$, which makes me feel kind of "perplexed."

Can you check and explain how to calculate this?

Thank you!

Since your average is above $90$, the worst case scenario for you is that the final examination is worth $20%$ of your grade. If you solve the equation you wrote for $x$, you will find the worst grade you could obtain on your final examination. Obviously, you should aim higher. — N. F. Taussig, May 19 '15 at 23:53

Christopher · Answer 1 · 2015-05-19T21:45:50.790

3

You want either

$(0.80 * 98) + (0.20 * x) = 90$

or

$(0.85 * 98) + (0.15 * x) = 90$

since the exam you have tomorrow and what you have done so far must add up to 100% of the mark.

edited May 19 '15 at 21:45

answered May 19 '15 at 21:43

Christopher

7,137

I need a mathematical percentage for a final exam grade, too see how many points I need for a $90\%$ average.

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