1 supra 120 + 2 supra 120 + 3 supra 20 + ....+119 supra 120 =

Răspuns :

1/120 + 2/120 + 3/20 + ....+119/120 =
=1/120
×(1+2+3+...+119)=
=1/120×(119×120)/2=
=1/120 ×119×60=
=119/2=59,5