Thread: Percentage help

Hi i hope i am putting this question in the correct forum so here goes.
Say someone has taken 4 tests over the year one test had 20 questions one had 54 questions one had 40 questions and a practical exam that represents 20% of the total mark.
If i have 4 percentages say 80%,70%,65% and 60%on the practical how do i add these numbers together to represent one total percentage.
I am no good at math and my son has asked me this question could someone please give me the formula and an explanation so as i may explain this to my son thank you.

It isn't possible to answer that question without further information. Specifically are each of the three tests equally weighted, or, for example, does the third test carry twice the weight (double the marks) of the first one, (having twice as many questions) ?
If the three tests are equally weighted, you can think of them as making up the remaining 80 marks out of a 100 left when the practical mark has been removed, and so worth 80/3 marks each. In that case the overall mark would be
(80% of 80/3) + (70% of 80/3) + (65% of 80/3) + (60% of 20)
which comes to about 69.33 out of 100 i.e. 69.33%.
If the tests are not equally weighted then you need to substitute other values (adding up to 80) for the three 80/3's.
There should be a module description form (or whatever the school or college choose to call it) defining how the module is to be assessed and that should contain the relevant information.

Thank you for replying.The first test is worth 20% the second 20% and the third 40% and as you know the practical is worth 20%.

In that case the overall mark (for the example figures that you give) would be
(80% of 20) + (70% of 20) + (65% of 40) + (60% of 20) = 68/100 (68%).

Thank you for all your help i did what you said and read the text book and your answers made it easy.I think i better go to class with my son.
Cheers Mick463