4+7+10+...+292+295+298等于多少
问题描述:
4+7+10+...+292+295+298等于多少
答
= (4+298)*294/2
= 44394
答
4+7+10+...+292+295+298 = (1+ 4+7+10+...+292+295+298)- 1
= (1+ 298)*100/2 -1 = 299* 50 -1 = 14949
答
4+7+10+...+292+295+298 = 3+1 + 3 +4 +3 +7 + ...+3 +289 + 3+ 292 + 3 + 295= 3 * 99 + 1+4+7+...+295= 3 * 99 + (1+295)*99/2= 297 + 148*99= 297 +14800 -148=14800+149=14949