(1)301+302+303+304+305
=303×5
=1515;
(2)392+681+433+790+894
=(300+600+400+700+800)+(90+80+30+90+90)+(2+1+3+0+4)
=2800+380+10
=3190;
(3)296+297+298+299+1+2+3+4
=(296+4)+(297+3)+(298+2)+(299+1)
=300+300+300+300
=1200;
(4)198+199+200+201+202
=200×5
=1000.