Math Is Fun Forum

leither

Member

Registered: 2009-06-24

Posts: 2

Percentages!

Hi Guys,

I need help pls...

I recently submitted three pieces of work for my class with the first being graded at 89% and worth 20% of my overall module mark.  The second test was marked at 90% and was worth 30% of my total overall mark.  However, I wasn't told of the mark for my final peice of submitted work which was worth 50% of my total grade.

My overall grade for the class was 80.6% so what was my mark for my final peice of work?

Can someone explain how I would work this out?

Thanks.

bobbym

bumpkin

From: Bumpkinland

Registered: 2009-04-12

Posts: 109,606

Re: Percentages!

Hi leither;

(.2)(89) + (.3)(90) + (.5)x = 80.6

x = 71.6 was the final mark

Last edited by bobbym (2009-06-24 09:26:56)

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In mathematics, you don't understand things. You just get used to them.
If it ain't broke, fix it until it is.
Always satisfy the Prime Directive of getting the right answer above all else.

mathsyperson

Moderator

Registered: 2005-06-22

Posts: 4,900

Re: Percentages!

You get the overall mark by multiplying each individual mark by its weight.

So, 80.6 = 89*0.2 + 90*0.3 + [Mark #3]*0.5

Rearranging this gives that you must have scored 71.6% on your third piece of work.

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Why did the vector cross the road?
It wanted to be normal.

leither

Member

Registered: 2009-06-24

Posts: 2

Re: Percentages!

Thanks