The formula given here is not exact : it is not an average, the notes take in account more the last scores than the first.
See
http://wims.auto.u-psud.fr/wims/lang=fr&+module=help%2Fstudent%2Fdocetud.fr&+job=read&+doc=1&+block=notes
Qn = (0.85 Qn-1 +Sn)/1.85 .
except that the second formula is false, but give an idea !
Bernadette
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