In Sam’s chemistry class, his final grade consists of lab wo

Sol: If you are good with weighted average concept then it shouldn't take you long

Here is how I would approach this problem.



It is given that Lab work exam has 2/3 weightage and final exam therefore will have weightage of 1/3
Therefore by weighted average ratio.

The final grade score of 75% will be twice as close to Lab exam average then final exam average

Now If total distance between Final exam and Lab exam is x
then x/3 will be distance between Lab exam score and Total final grade score and
2x/3 will be distance between final exam score and Total final grade score

Given x/3 =5 so x= 15

and therefore 2x/3 =10. So Final exam score will be 10 less than grade score of percentage of 75 ie. 75-10= 65%

Ans is A.

Another way to do it will be

\(\frac{W1}{W2}\)= \(\frac{(A2- Avg)}{(Avg- A1)}\)

W1=1/3
W2=2/3

So W1/W2= 1/2
\(\frac{1}{2}\) = \(\frac{(80-75)}{(75-x)}\)

1/2 = 5/(75-x)

75-x=10 or x =65%

For more on weighted average concept..Check out Veritas prep blog:

https://www.gmatclub.com/forum/veritas-prep-resource-links-no-longer-available-399979.html#/2011/04 ... ge-brutes/
https://www.gmatclub.com/forum/veritas-prep-resource-links-no-longer-available-399979.html#/2011/03 ... -averages/