24道,加法交换律两个加数交换的略.124 + 876 = 1000 126 + 874 = 1000 143 + 857 = 1000 147 + 853 = 1000 153 + 847 = 1000 157 + 843 = 1000 174 + 826 = 1000 176 + 824 = 1000 214 + 786 = 1000 216 + 784 = 1000 284 + 716 = 1000 286 + 714 = 1000 342 + 658 = 1000 348 + 652 = 1000 352 + 648 = 1000 358 + 642 = 1000 413 + 587 = 1000 417 + 583 = 1000 432 + 568 = 1000 438 + 562 = 1000 462 + 538 = 1000 468 + 532 = 1000 483 + 517 = 1000 487 + 513 = 1000