Help with what is probably a very simple problem!

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teri

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Hi, I am probably just being really dense, but my friends and I cannot work this out...

I am studying a module at uni and the assessments are essays, the first essay was weighted at 40% within the module and my friend scored 35%. The second essay is weighted at 60% within the module. What % does he have to score in the second essay to average at 40% overall in the module??

We know that if it was split 50/50 then he would have to score 45% to average at 40%, but as it is a 40/60 split we are totally lost and confused! I need an explanation so that we can apply the same math to all our scores!

Please help!
 
teri said:
Hi, I am probably just being really dense, but my friends and I cannot work this out...

I am studying a module at uni and the assessments are essays, the first essay was weighted at 40% within the module and my friend scored 35%. The second essay is weighted at 60% within the module. What % does he have to score in the second essay to average at 40% overall in the module??

We know that if it was split 50/50 then he would have to score 45% to average at 40%, but as it is a 40/60 split we are totally lost and confused! I need an explanation so that we can apply the same math to all our scores!

Please help!
Click to expand...

say your freind needs to score = x %

then

40/100 * 35/100 + 60/100 * x/100 = 40/100

0.144 + 0.006 * x = 0.4

x = (0.4 - 0.144)/0.006

Now finish it...
 
Sorry, I could cry with the frustration of not understanding this!

By that calculation, the answer is that he needs to score 43.333 (or 44% to be realistic) to average at 40% for the module... however, that is less than he would need (45%)if the essays were equally weighted at 50/50, surely the answer will be that he needs a higher score than 45%, otherwise what is the point of weighting the second essay at more than the first?

I worry that maybe I am not understanding the fundamental basics of this though as I cannot get 60/100 to equal 0.006 either!! Why is it not 0.6??
 
teri said:
Sorry, I could cry with the frustration of not understanding this!

By that calculation, the answer is that he needs to score 43.333 (or 44% to be realistic) to average at 40% for the module... however, that is less than he would need (45%)if the essays were equally weighted at 50/50, surely the answer will be that he needs a higher score than 45%, otherwise what is the point of weighting the second essay at more than the first?

I worry that maybe I am not understanding the fundamental basics of this though as I cannot get 60/100 to equal 0.006 either!! Why is it not 0.6??

No it is not - read it carefully!! I wrote

\(\displaystyle \frac{60}{100} \cdot\ \frac{x}{100}\)

\(\displaystyle = \ \frac{60}{100*100} \cdot\ x\)

\(\displaystyle = \ 0.006 \cdot\ x\)

get it now......
Click to expand...

He needs to score 3.333 points higher than the goal (40). These 3.333 points will count more when it is taken in as 60% - compared to 50% weight. Think about it this way

If the second test was 100% - he would have to score 40.

Suppose the first score counted 20% - then the contribution from first score would be 7. He would have to score [(40-7)/0.8 = ] 41.25 to get an average of 40.

Higher the weight of the second test - less he has to score to make up the deficiency.
 
aaaah!! I understand!

But it seems so strange that my friend actually needs to score less on this second assignment than he would have if the two had equal weighting, especially as the reason our lecturer has split the weighting like this is to make us work harder on this second assignment! She has told my friend that he needs to score in at least the 60%+ bracket if he has any hope of passing the module (a pass is 40% overall). We weren't sure about that which is why we have all been trying to work out the maths!

But if I do understand it correctly, then we don't actually have to worry so much, he can score 44% on this second assignment and still pass the module at 40% overall? We have been so confused about this!I actually scored 85% on the first assignment and so to average at 85% overall I need to score 84% on the second assignment, is that right??
 
teri said:
aaaah!! I understand!

But it seems so strange that my friend actually needs to score less on this second assignment than he would have if the two had equal weighting, especially as the reason our lecturer has split the weighting like this is to make us work harder on this second assignment! She has told my friend that he needs to score in at least the 60%+ bracket if he has any hope of passing the module (a pass is 40% overall). We weren't sure about that which is why we have all been trying to work out the maths!

But if I do understand it correctly, then we don't actually have to worry so much, he can score 44% on this second assignment and still pass the module at 40% overall? We have been so confused about this!I actually scored 85% on the first assignment and so to average at 85% overall I need to score 84% on the second assignment, is that right??
Click to expand...

Watch that!!!

Assuming 40/60 weight like before:

0.4*0.85 + 0.6*0.84 = 0.844 (not quite 0.850)
 
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