a) 334+66 = 333+66+1 = 399+1 = 400
b) 127+273 = 127+3+270=130+270 = 370+30 = 400
c) 993+2107 = 993+7+2100 = 1000+2100 = 3000
d)4672+1325 = 4000+1000+600+300+70+20+2+5 = 5000+900+90+7 = 5997
e)35275+24725 = 35000+24000+270+720+5+5 = 59000+990+10 = 59990+10 = 60000