6+101+11+96+...=107+107+...+107
cati de 107 avem?
cate nunmere avem?
avem (101-6)/5 +1=95/5+1=19+1=20 de numere
deci 10 perechi
deci 10 de 107 deci 10*107=1070
altfel
6=1+5*1
11=1+5*2
16=1+5*3
21=1+5*4
..................
101=1+5*20
adunma tot= 1=1+...+1 (20de 1) +5(1+2+3+...+20)=
20+5*20*21/2=
20+50*21=
20+1050=
1070