571
First, add the digits other than the units, 490 + 70 = 560. Remember that for a moment. Now, add the one's digits, 7 + 4 = 11. Now, add the 11 to the 560 to get 571. ---- Alternately, subtract 3 from 74 and give it to 497, so we have 500 + 71 = 571.