Notam cu e1,e2,e3,.....,e25- notele celor 25 de elevi.
media aritmetica a notelor tuturor 25: (e1+e2+..+e25)/25=7,25. De aici rezulta ca e1+e2+...+e25=7,25 * 25=181,25(suma notelor celor 25 de elevi)
media artimetica a primilor 10: (e1+e2+...+e10)/10=6,80.De aici rezula ca
e1+e2+..+e10=6,80*10=68(suma notelor primilor 10 elevi)
25-10=15 elevi ramasi
181,25-6,80=113,25(suma notelor celor 15 elevi ramasi)
media aritmetica a celor 15 elevi ramasi: 113,25/15=7,55
Succes! :)