\[\boxed{\mathbf{1.}}\]
\[500 =\]
\[489 + 11\]
\[494 + 6\]
\[499 + 1\]
\[488 + 12\]
\[479 + 21\]
\[498 + 2\]
\[492 + 8\]
\[\boxed{\mathbf{2.}}\]
\[1)\ 73 + 127 = 200\]
\[64 + 36 = 100\]
\[215 + 195 = 400\]
\[46 + 354 = 400\]
\[188 + 412 = 600\]
\[227 + 73 = 300\]
\[165 + 5 = 200\]
\[2)\ 333 + 67 = 400\]
\[182 + 518 = 700\]
\[299 + 101 = 400\]
\[663 + 37 = 700\]
\[485 + 115 = 600\]
\[47 + 53 = 100\]
\[115 + 35 = 150\]
\[250 + 270 = 520\ \]
\[\boxed{\mathbf{3.}}\]
\[136 + 464 + 98 = 600 + 98 =\]
\[= 698\]
\[287 + 55 + 413 = 700 + 55 =\]
\[= 755\]
\[105 + 438 + 362 =\]
\[= 800 + 105 = 905\]
\[589 + 67 + 311 = 900 + 67 =\]
\[= 967\]