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Calculati:
1,11+1,12+...+1,30=?


Răspuns :

1,11+1,12+...+1,30=
=1+11/100+1+12/100+....+1+30/100=
nr de termeni 30-11+1=20
=1×20+1/100(11+12+...+30)=
=20+1/100(10+1+10+2+...+10+20)=
=20+1/100(10×20+1+2+...+20)=
=20+1/100(200+20×21/2)=
=20+1/100(200+210)=
=20+1/100 ×410=
=20+4,1=24,1