用简便方法计算31十32十33十34十35十36十37十38十39

（31+39）乘以4+35=280+35=315

31+32+33+34+35+36+37+38+39
=（31+39）+（32+38）+（33+37）+（34+36）+35
=70+70+70+70+35
=70×4+35
=280+35
=315本回答被网友采纳

31+32+33+34+35+36+37+38+39
=35×9
=35×10-35×1
=350-35
=315