S=1+2+3+.....1500= 1500+1501/2=1 125 750
S=1000+1001+1002+....5400 = 5400*5401/2 - 999*1000/2=14582700-
-499500=14083200
S= 2+4+6+.....6000= 2*(1+2+3+...3000)=2*3000*30001/2=90003000
S=800+802+804+...1400=1400*1401/2- 799*800/2=980700-319600=
= 661100
S=5+10+15+......7500= 5*(1+2+3+.....+1500)=5* 1500*1501/2= 5628750